Method and systems for polymer recycling

Abstract

Methods for recycling and depolymerizing polymeric materials are disclosed. A mechanical force is applied to a polymeric material in the presence of a small molecule chain transfer agent to induce mechanoradical formation and capture, introducing chain-end functionality. The functionalized polymer can then be contacted with one or more radically polymerizable monomers under conditions effective to repolymerize the material, for example by chain extension or block copolymer formation via controlled radical processes such as RAFT or ATRP. In other aspects, the functionalized or mechanically degraded polymer is heated at a temperature below about 400 °C, such as below about 300 °C, to depolymerize at least a portion of the material to its original monomer. The methods can be implemented as solvent-free processes and are applicable to polymers including polystyrene, polyolefins, poly(meth)acrylates, polyvinyl chloride, polyvinyl acetate, and blends thereof.

Description

[0001] Attorney Docket No. 10975-084W01

[0002] CSURF Ref.: 2024-097 METHOD AND SYSTEMS FOR POLYMER RECYCLING

[0003] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims benefit of priority of U.S. Provisional Application No.

[0004] 63 / 791,361, filed April 18, 2025, which is incorporated herein by reference in its entirety.

[0005] BACKGROUND

[0006] Polymeric materials are indispensable in modern life and are used in a wide range of consumer and industrial products, leading to steadily increasing plastic production and waste generation worldwide. Despite the recognized need for sustainable end-of-life options, only a small fraction of plastic waste is currently recycled, and most discarded polymers are landfilled or incinerated, driving continued demand for virgin, fossil-derived feedstocks. Mechanical recycling by melt reprocessing is the predominant industrial strategy, but the combination of thermal and shear forces during extrusion and related processes causes chain scission, lowers molecular weight, broadens molecular weight distributions, and degrades mechanical performance so that the recycled materials are typically downcycled into lower-value products.

[0007] Accordingly, there remains a need for recycling approaches that can operate within or alongside existing mechanical processing infrastructure to mitigate degradation, enhance the value of recycled polymers, and, in some cases, enable more energy-efficient routes to polymer re-use or monomer recovery.

[0008] SUMMARY

[0009] Described herein are methods that improve the recycling of polymeric materials by leveraging the polymer degradation that occurs under mechanical force. Example mechanical degradation methods that may be used in conjunction with the methods described herein include ball milling and ultrasonication. When bonds break, highly reactive, short-lived radicals are formed. These mechanoradicals can then be captured using small molecule chain transfer agents (CTAs), ultimately introducing accessible functionalities to degraded polymer chains. Once functionalized with these CTAs, these degraded polymers can subsequently be chain extended or depolymerized back into monomer - hence improving the recyclability of the material.Attorney Docket No. 10975-084W01

[0010] CSURF Ref.: 2024-097 Mechanoradicals generated from ball milling polyethylene can catalyze small molecule dehalogenation reactions. Mechanoradicals generated from polystyrene can also be captured by small molecules that act as fluorescent labels. However, chain transfer agents have not been used for mechanoradical capture of polymers, and it has not been shown that this method can be used for repolymerization or depolymerization of these functionalized polymers.

[0011] In some examples described herein, these radicals are captured with trithiocarbonates (TTCs), copper halides, and phthalimides. TTCs are traditionally used in reversible addition fragmentation chain transfer (RAFT) polymerizations to control the concentration of reactive radical species, and hence control the polymerization. Thus, these functionalized polymers can be employed as macroinitiators for controlled polymerization, generating higher molecular weight materials akin to virgin polymers. These macroinitiators can also be copolymerized with different monomers to create block copolymer compatibilizers, a macromolecule that stabilizes insoluble polymer blends.

[0012] It has additionally been shown that polymers both with these TTC, halogen, and phthalimide end groups can access depolymerization to monomer at significantly lower temperatures than their unfunctionalized counterparts. Thus, these functionalities can be introduced through mechanoradical capture during ball milling so that waste polymers can then be depolymerized at lower temperatures. The resulting monomer can then be used to make new materials.

[0013] Copper halides would introduce a halogen functionality to the degraded polymer chain. Halide chain ends can be used for atom transfer radical polymerization (ATRP), a type of controlled radical polymerization. Thus, using these small molecules for mechanoradical capture offers another pathway for repolymerization of degraded polymer to higher molecular weight, more desirable materials.

[0014] By taking advantage of the radical formation innate to mechanical recycling, functionalization may be introduced using CTAs. Thus, higher value products may result from mechanical recycling, offering a promising path toward reducing plastic waste.

[0015] These methods can help address issues with recycling of polymer waste by allowing the polymers to be remade into high-value materials. Trithiocarbonate chain transfer agents and copper halides, both traditionally used in controlled radical polymerizations, can stabilize andAttorney Docket No. 10975-084W01

[0016] CSURF Ref.: 2024-097 capture radicals. Introducing these functionalities during the mechanical recycling process can allow for chain extension that would otherwise not be possible. In addition, trithiocarbonate, halogen, and phthalimide end groups can be used labile groups that allow for depolymerization to monomer at more accessible temperatures. Thus, these methods can be used to generate both higher molecular weight materials akin to virgin polymers and producing monomers that can be repolymerized, offering a promising path toward a circular plastic economy.

[0017] Further, these methods can be solvent-free and use recycling infrastructure already in place to recycle polymers in a more efficient manner. Mechanoradicals are formed regardless of polymer type, so this method is widely applicable. Once functionalization is achieved, depolymerization to monomer, chain extension to make a homopolymer, and chain extension to make a block copolymer are possible.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying figures, which are incorporated in and constitute a part of this specification, illustrate several aspects described below.

[0020] Figure 1A. Formation of radicals under mechanical forces leads to the deterioration of material properties.

[0021] Figure IB. Examples of polymer radical capture for chain extension or depolymerization.

[0022] Figure 1C. Examples of mechanoradical capture with a small molecule chain transfer agent (e.g., a trithiocarbonate such as bisTTC) for applications in repolymerization, copolymerization, and depolymerization.

[0023] Figure 2A. DRI traces showing PS milled neat, milled with TTC, and milled with TTC and styrene.

[0024] Figure 2B. DRI traces showing PMMA milled neat, milled with TTC, and milled with TTC and MMA.

[0025] Figure 3. Thermogravimetric analysis (TGA) of PMMA before (black) and after (red) ball milling. Ball-milled PMMA shows significant weight loss beginning at substantially lower temperatures than pristine PMMA, consistent with early onset of thermal depolymerization. This shift is attributed to the formation of unsaturated chain ends during milling, likely introduced via radical. PMMA can depolymerized back to its starting monomer, however this is usually done at very high temperatures. In the graph, before ballAttorney Docket No. 10975-084W01

[0026] CSURF Ref.: 2024-097 milling the sample, this is only -5% mass loss at 220 °C over 200 minutes. However, once ball milling is done on the sample, there is significant depolymerization occurring at much lower temperatures. The ball milled sample showed -55% mass loss under the same conditions.

[0027] Figure 4A. DRI and UV absorbance at 310 nm measured with SEC of macroinitiator PS chain extended by RAFT polymerization to its original molecular weight.

[0028] Figure 4B. DRI and UV absorbance at 310 nm measured with SEC of macroinitiator PS copolymerized with MMA to form a diblock polymer.

[0029] Figure 5. Temperature-dependent oscillatory shear rheology of pristine (black) and ball-milled (gray) PMMA samples, with corresponding loss moduli shown in red.

[0030] Figure 6. Schematic illustrating aspects of the methods described herein.

[0031] DETAILED DESCRIPTION

[0032] The following description of the disclosure is provided as an enabling teaching of the disclosure in its best, currently known embodiments. Many modifications and other embodiments disclosed herein will come to mind to one skilled in the art to which the disclosed compositions and methods pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosures are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. The skilled artisan will recognize many variants and adaptations of the aspects described herein. These variants and adaptations are intended to be included in the teachings of this disclosure and to be encompassed by the claims herein.

[0033] Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0034] As can be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure.

[0035] Any recited method can be carried out in the order of events recited or in any other order that is logically possible. That is, unless otherwise expressly stated, it is in no way intended that any method or aspect set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not specifically stateAttorney Docket No. 10975-084W01

[0036] CSURF Ref.: 2024-097 in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps or operational flow, plain meaning derived from grammatical organization or punctuation, or the number or type of aspects described in the specification.

[0037] All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided herein can be different from the actual publication dates, which can require independent confirmation.

[0038] It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosed compositions and methods belong. It can be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0039] Prior to describing the various aspects of the present disclosure, the following definitions are provided and should be used unless otherwise indicated. Additional terms may be defined elsewhere in the present disclosure.

[0040] Definitions

[0041] As used herein, “comprising” is to be interpreted as specifying the presence of the stated features, integers, steps, or components as referred to, but does not preclude the presence or addition of one or more features, integers, steps, or components, or groups thereof. Moreover, each of the terms “by”, “comprising,” “comprises”, “comprised of,” “including,” “includes,” “included,” “involving,” “involves,” “involved,” and “such as” are used in their open, non-limiting sense and may be used interchangeably. Further, the term “comprising” is intended to include examples and aspects encompassed by the terms “consisting essentially of’ and “consisting of.” Similarly, the term “consisting essentially of’ is intended to include examples encompassed by the term “consisting of.”Attorney Docket No. 10975-084W01

[0042] CSURF Ref.: 2024-097 As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a compound”, “a composition”, or “a disorder”, includes, but is not limited to, two or more such compounds, compositions, or disorders, and the like.

[0043] It should be noted that ratios, concentrations, amounts, and other numerical data can be expressed herein in a range format. It can be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it can be understood that the particular value forms a further aspect. For example, if the value “about 10” is disclosed, then “10” is also disclosed.

[0044] When a range is expressed, a further aspect includes from the one particular value and / or to the other particular value. For example, where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure, e.g., the phrase “x to y” includes the range from ‘x’ to ‘y’ as well as the range greater than ‘x’ and less than ‘y’. The range can also be expressed as an upper limit, e.g., ‘about x, y, z, or less’ and should be interpreted to include the specific ranges of ‘about x’, ‘about y’, and ‘about z’ as well as the ranges of ‘less than x’, less than y’, and ‘less than z’. Likewise, the phrase ‘about x, y, z, or greater’ should be interpreted to include the specific ranges of ‘about x’, ‘about y’, and ‘about z’ as well as the ranges of ‘greater than x’, greater than y’, and ‘greater than z’. In addition, the phrase “about ‘x’ to ‘y’”, where ‘x’ and ‘y’ are numerical values, includes “about ‘x’ to about ‘y’”.

[0045] It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a numerical range of “about 0.1% to 5%” should be interpreted to include not only the explicitly recited values of about 0.1% to about 5%, but also include individual values (e.g., about 1%, about 2%, about 3%, and about 4%) and the sub-ranges (e.g., about 0.5% to about 1.1%; about 5% to about 2.4%; about 0.5% to aboutAttorney Docket No. 10975-084W01

[0046] CSURF Ref.: 2024-097 3.2%, and about 0.5% to about 4.4%, and other possible sub-ranges) within the indicated range.

[0047] As used herein, the terms “about,” “approximate,” “at or about,” and “substantially” mean that the amount or value in question can be the exact value or a value that provides equivalent results or effects as recited in the claims or taught herein. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact but may be approximate and / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art such that equivalent results or effects are obtained. In some circumstances, the value that provides equivalent results or effects cannot be reasonably determined. In such cases, it is generally understood, as used herein, that “about” and “at or about” mean the nominal value indicated ±10% variation unless otherwise indicated or inferred. In general, an amount, size, formulation, parameter or other quantity or characteristic is “about,” “approximate,” or “at or about” whether or not expressly stated to be such. It is understood that where “about,” “approximate,” or “at or about” is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise. As used herein, the term “substantially free,” when used in the context of a composition or component of a composition that is substantially absent, is intended to refer to an amount that is then about 1 % by weight or less, e.g., less than about 0.5 % by weight, less than about 0.1 % by weight, less than about 0.05 % by weight, or less than about 0.01 % by weight of the stated material, based on the total weight of the composition.

[0048] As used herein, the term “polymeric material” refers to a material comprising one or more polymers, including homopolymers, copolymers (e.g., random, block, graft, alternating), terpolymers, and blends or mixtures thereof, and may include additives such as fillers, plasticizers, stabilizers, or pigments. A “polymer” refers to a macromolecule formed by the polymerization of one or more monomers and encompasses linear, branched, crosslinked, or network architectures.

[0049] As used herein, the term “mechanical recycling” refers to any process in which a polymeric material is physically processed and re-formed, without full chemical depolymerization to monomer, and includes processes such as grinding, extrusion, pelletizing, re-melting, molding, ball milling, ultrasonication, and combinations thereof.Attorney Docket No. 10975-084W01

[0050] CSURF Ref.: 2024-097 As used herein, the term “mechanical force” refers to a force applied to a polymeric material that induces deformation or fracture of polymer chains, including but not limited to impact, shear, compression, tension, cavitation, or combinations thereof, as can be generated, for example, in ball milling, grinding, extrusion, mastication, or ultrasonication.

[0051] As used herein, the term “mechanoradical” refers to a radical species generated in a polymeric material as a result of the application of mechanical force to the polymer chains, for example, during ball milling, ultrasonication, extrusion, or other mechanical processing. “Mechanoradical formation” refers to the generation of such radical species under mechanical force, and “mechanoradical capture” refers to the reaction of such radical species with another species, such as a small molecule chain transfer agent, to form a covalently modified polymer chain.

[0052] As used herein, the term “mechanical degradation” refers to a reduction in the degree of polymerization or molecular weight of a polymeric material due to the application of mechanical force, for example resulting in a decrease in number-average molecular weight Mnand / or an increase in molecular weight dispersity relative to the starting polymer. “Chain scission” refers to the cleavage of covalent bonds along the polymer backbone, producing shorter polymer chains.

[0053] As used herein, the term “small molecule chain transfer agent” or “chain transfer agent (CTA)” refers to a non-polymeric, typically low-molecular- weight compound that can react with a radical species to form a new radical and thereby transfer radical character, and includes, for example, trithiocarbonates, dithioesters, dithiocarbamates, and combinations thereof. In certain aspects, the small molecule chain transfer agent is a trithiocarbonate such as bis(butyl trithiocarbonate), a bis(trithiocarbonate) disulfide, or a RAFT agent such as cyanopropyl butyl trithiocarbonate.

[0054] As used herein, the term “trithiocarbonate” refers to a compound comprising a — S-C(=S)-S- moiety, optionally as part of a bis(trithiocarbonate) disulfide, and encompasses structures commonly used as RAFT agents or precursors thereto. The term “bis(trithiocarbonate)” or “bisTTC” refers to a compound in which two tri thiocarbonate units are linked, for example, bis(butyl trithiocarbonate) as described in the Examples.

[0055] As used herein, the term “copper halide” refers to a copper-containing compound comprising a halide anion, such as CuCl, CuBr, Cui, CuCh, CuBi’2, and mixtures thereof, which can provide halogen functionality at a polymer chain end and can serve as an initiator or macroinitiator in atom transfer radical polymerization (ATRP).Attorney Docket No. 10975-084W01

[0056] CSURF Ref.: 2024-097 As used herein, the term “phthalimide” refers to a phthalimide-containing compound or functional group capable of being introduced at a polymer chain end, including phthalimide moieties that can influence depolymerization or other reactivity of the polymer.

[0057] As used herein, the term “radically polymerizable monomer” refers to a monomer that can undergo free-radical or controlled radical polymerization, including but not limited to vinyl, allylic, acrylate, methacrylate, styrenic, and related unsaturated monomers (e.g., ethylenically unsaturated monomers) such as styrene, methyl methacrylate (MMA), other methacrylates, acrylates, acrylonitrile, vinyl chloride, and vinyl acetate.

[0058] As used herein, the term “macroinitiator” refers to a polymeric species bearing one or more chain-end functionalities that can initiate or mediate radical polymerization of a monomer under suitable conditions, such as a polymer functionalized with a trithiocarbonate, halogen, or phthalimide end group capable of participating in RAFT polymerization, ATRP, or other controlled radical processes.

[0059] As used herein, the term “RAFT polymerization” or “reversible additionfragmentation chain transfer polymerization” refers to a controlled radical polymerization process involving a chain transfer agent, such as a trithiocarbonate, that mediates an equilibrium between active and dormant chains to afford polymers with controlled molecular weight and narrow dispersity. As used herein, the term “ATRP” or “atom transfer radical polymerization” refers to a controlled radical polymerization process in which a halogen-containing initiator or macroinitiator (e.g., a halogen-terminated polymer chain) participates in a reversible activation-deactivation cycle mediated by a transition metal catalyst such as a copper halide.

[0060] As used herein, the term “repolymerizing the polymeric material” refers to subjecting a mechanoradical-functionalized or CTA-functionalized polymeric material to conditions effective to increase its molecular weight and / or to polymerize one or more additional monomers from the functionalized chain ends, for example by RAFT polymerization, ATRP, or another controlled radical polymerization, to form a higher-molecular-weight homopolymer or block copolymer.

[0061] As used herein, the term “block copolymer” refers to a copolymer comprising two or more distinct blocks of differing composition connected in sequence, such as a polystyrene-block-poly(methyl methacrylate) copolymer. A “block copolymer compatibilizer” refers to a block copolymer that, when present in a blend of two or more otherwise incompatible polymers, improves the miscibility, interfacial adhesion, or morphology of the blend.Attorney Docket No. 10975-084W01

[0062] CSURF Ref.: 2024-097 As used herein, the term “depolymerization” refers to a process in which a polymeric material is converted, at least in part, back to its constituent monomer(s) or lower-molecular-weight species under thermal or other conditions, for example as evidenced by a decrease in polymer mass and corresponding evolution of monomer detected by analytical techniques such as thermogravimetric analysis (TGA) and mass spectrometry. “Bulk depolymerization” refers to such depolymerization carried out on a solid or melt-phase polymer sample rather than in highly dilute solution.

[0063] As used herein, the term “ceiling temperature” refers to the temperature at which the rates of polymerization and depolymerization of a given monomer-polymer system are equal, such that the polymer is in equilibrium with its monomer and above which depolymerization is thermodynamically favored. A “reduced depolymerization temperature” refers to a depolymerization temperature that is lower than that of a corresponding polymer lacking the functional group(s) described herein, such as TTC, halogen, or phthalimide end groups.

[0064] As used herein, the term “vinyl-terminated chain end,” “unsaturated chain end,” or “vinylidene moiety” refers to a terminal unsaturated group on a polymer chain, for example a \text {-CH\(_.2=C(R)-}) or related structure, that can facilitate unzipping depolymerization under thermal conditions.

[0065] As used herein, the term “solvent-free” refers to a process or composition in which no solvent is intentionally added, and any solvent present is at most an incidental or residual amount, for example less than about 5 wt%, less than about 1 wt%, or less than about 0.5 wt% of the total weight of the polymeric material being processed. In some aspects, “solvent-free” conditions correspond to an η-parameter below a threshold at which liquid-assisted grinding significantly suppresses mechanical degradation.

[0066] As used herein, the term “liquid-assisted grinding” or “LAG” refers to ball milling or related mechanical processing performed in the presence of an added liquid, characterized by an η-parameter (ratio of solvent volume to solid mass) within a regime in which the added liquid measurably alters the extent of chain scission, for example inhibiting degradation at i] values greater than about 0.2 as described in the Examples.

[0067] The present disclosure provides methods and systems for recycling and depolymerizing polymeric materials by applying mechanical force to induce mechanoradical formation in the presence of small molecule chain transfer agents, thereby capturing mechanoradicals and introducing chain-end functionality that can be used forAttorney Docket No. 10975-084W01

[0068] CSURF Ref.: 2024-097 repolymerization, copolymerization, and / or depolymerization to monomer at reduced temperatures. In certain aspects, the methods can be implemented as solvent-free processes and can be integrated into existing mechanical recycling infrastructure so that polymeric materials can be remade into higher- value products instead of being downcycled.

[0069] In some embodiments, methods for recycling a polymeric material can comprise applying a mechanical force to the polymeric material to induce mechanoradical formation in the presence of a small molecule chain transfer agent, thereby capturing mechanoradicals formed by the applied mechanical force. The polymeric material can be any material comprising one or more polymers, such as a homopolymer, copolymer, or blend, and may include additives such as fillers, stabilizers, or pigments. The polymeric material can comprise a polymer formed by polymerization (e.g., radical polymerization) of an unsaturated monomer (e.g., an ethylenically unsaturated monomer). In some embodiments, the polymeric material comprises polystyrene, a polyolefin, a poly(meth)acrylate, polyvinyl chloride, polyvinyl acetate, a copolymer thereof, or a blend thereof.

[0070] The mechanical force can be applied by any suitable operation that generates mechanoradicals in the polymeric material, including but not limited to ball milling, ultrasonication, extrusion, grinding, mastication, kneading, calendering, or combinations thereof. In certain embodiments, applying the mechanical force comprises ball milling the polymeric material, for example in a planetary or mixer ball mill using metallic, ceramic, or other grinding media. In other embodiments, applying the mechanical force comprises ultrasonication of a solution or dispersion of the polymeric material. In further embodiments, applying the mechanical force comprises extrusion, such as single-screw or twin-screw extrusion of the polymeric material in the presence of a small molecule chain transfer agent.

[0071] In some embodiments, the small molecule chain transfer agent comprises a trithiocarbonate, a copper halide, a phthalimide, a dithioester, a dithiocarbamate, or a combination thereof. In particular embodiments, the small molecule chain transfer agent comprises a trithiocarbonate, such as bis(butyl trithiocarbonate), a bis(trithiocarbonate) disulfide, or a RAFT-type trithiocarbonate such as cyanopropyl butyl trithiocarbonate. In other embodiments, the small molecule chain transfer agent comprises a copper halide such as CuCl, CuBr, Cui, CuCh, or CuBi’2, which can introduce halide chain ends suitable for atom transfer radical polymerization (ATRP). In still other embodiments, the small molecule chain transfer agent comprises a phthalimide-containing compound capable of adding to mechanoradicals and lowering depolymerization ceiling temperatures.Attorney Docket No. 10975-084W01

[0072] CSURF Ref.: 2024-097 In some embodiments, the polymeric material comprises a polyolefin, such as polyethylene or polypropylene, and the small molecule chain transfer agent comprises a trithiocarbonate, a copper halide, or a phthalimide. In some embodiments, the polymeric material comprises polystyrene and the small molecule chain transfer agent comprises a trithiocarbonate, a copper halide, or a phthalimide. In some embodiments, the polymeric material comprises poly(methyl methacrylate) or another poly(meth)acrylate and the small molecule chain transfer agent comprises a trithiocarbonate, a copper halide, or a phthalimide.

[0073] The ratio of the small molecule chain transfer agent to polymeric material can vary depending on the desired degree of functionalization. In some non-limiting embodiments, the polymeric material is contacted with from about 0.01 wt% to about 50 wt% of the small molecule chain transfer agent, such as from about 0.03 wt% to about 20 wt%, from about 0.05 wt% to about 10 wt%, or from about 0.1 wt% to about 5 wt%, based on the weight of the polymeric material. The Examples demonstrate incorporation of trithiocarbonate functionalities in polystyrene and PMMA when milled with 0.03 wt%, 0.05 wt%, 10 wt%, 20 wt%, or 50 wt% of bis(butyl trithiocarbonate).

[0074] In some embodiments, the method further comprises repolymerizing the polymeric material. Repolymerization can be performed after the step of applying mechanical force in the presence of the chain transfer agent, and can involve contacting the functionalized polymeric material with a radically polymerizable monomer under conditions effective to polymerize the radically polymerizable monomer with the polymeric material. In some embodiments, repolymerizing comprises performing a RAFT polymerization or an ATRP process, as described in further detail below.

[0075] In some embodiments, the method can comprise a solvent-free process. As used herein, solvent-free conditions refer to the absence of intentionally added solvent, with any solvent present being residual or incidental, and in some embodiments corresponding to less than about 5 wt% solvent, less than about 2.5 wt% solvent, less than about 1 wt% solvent, less than about 0.5 wt% solvent, or less than about 0.1 wt% solvent, based on the total weight of the polymeric material. In some embodiments, the method comprises ball milling the polymeric material and the small molecule chain transfer agent without any added solvent, thereby achieving mechanoradical formation and capture in the bulk polymer.

[0076] In some embodiments, small amounts of liquid may be added intentionally (liquid- assisted grinding, LAG) and are characterized using an η-parameter that describes the ratio of solvent volume to solute mass. The Examples demonstrate that increasing the η-parameterAttorney Docket No. 10975-084W01

[0077] CSURF Ref.: 2024-097 above about 0.2 with t-butanol significantly inhibits degradation and reduces functionalization, consistent with plasticization and energy dissipation, whereas η values below about 0.2 permit substantial chain scission and functionalization. Accordingly, in some embodiments, the method is carried out with an η-parameter less than about 0.2 to promote mechanoradical formation and capture, whereas in other embodiments higher η values are used to modulate the extent of degradation.

[0078] In some embodiments, after mechanoradicals have been captured by the small molecule chain transfer agent to generate a functionalized polymeric material, the method further comprises repolymerizing the polymeric material to increase its molecular weight and / or to form block copolymers. Repolymerization can involve contacting the functionalized polymeric material with a radically polymerizable monomer and subjecting the mixture to conditions effective to initiate and sustain radical polymerization.

[0079] In some embodiments, the radically polymerizable monomer is selected from the group consisting of styrene, a methacrylate, an acrylate, acrylonitrile, vinyl chloride, vinyl acetate, and combinations thereof. In particular embodiments, the radically polymerizable monomer comprises styrene or methyl methacrylate. The monomer can be the same as the monomer from which the polymeric material was originally formed (for homopolymer chain extension) or can be a different monomer (for block copolymer formation).

[0080] In some embodiments, the small molecule chain transfer agent is a RAFT-type trithiocarbonate, and repolymerizing the polymeric material comprises performing a RAFT polymerization in which the functionalized chains act as macro chain transfer agents (macroinitiators). For example, polystyrene that has been degraded and functionalized with trithiocarbonate end groups by ball milling in the presence of bis(butyl trithiocarbonate) can be dissolved in a solvent such as 1,4-dioxane together with styrene monomer, degassed, and irradiated with blue LED light to initiate RAFT polymerization. Under such conditions, the functionalized polystyrene can be chain extended to reach a number-average molecular weight comparable to or greater than its original molecular weight prior to mechanical degradation, as demonstrated by SEC with light scattering and UV detection at 310 nm.

[0081] In other embodiments, the functionalized polymeric material is used as a macroinitiator or macro chain transfer agent for forming block copolymers by copolymerization with a different monomer. For example, a functionalized polystyrene comprising trithiocarbonate end groups generated during ball milling can be chain extended with methyl methacrylate to yield a polystyrene-block-PMMA diblock copolymer, which isAttorney Docket No. 10975-084W01

[0082] CSURF Ref.: 2024-097 confirmed by SEC with dual refractive index and UV detection. Conversely, a functionalized PMMA comprising trithiocarbonate end groups can be chain extended with styrene to form a PMMA- block-poly styrene block copolymer. The resulting block copolymers can be used as block copolymer compatibilizers in polymer blends, such as blends of polystyrene and PMMA, to improve interfacial adhesion and morphology.

[0083] In some embodiments, repolymerizing the polymeric material restores at least a portion of the original mechanical properties of the starting polymer. For example, rheological measurements of PMMA before ball milling, after ball milling, and after RAFT-based chain extension show that the ball-milled sample exhibits a reduced glass transition temperature and loss of rubbery plateau, consistent with molecular weight below the entanglement threshold, whereas the chain-extended sample recovers a rubbery plateau and mechanical behavior more similar to the pristine polymer.

[0084] In additional embodiments, the small molecule chain transfer agent is a copper halide, and repolymerizing the polymeric material comprises atom transfer radical polymerization (ATRP) from halide-terminated chain ends introduced during mechanoradical capture. In such embodiments, a copper halide-functionalized polymer acts as a macroinitiator for ATRP of a radically polymerizable monomer such as styrene or an acrylate, in the presence of a suitable ligand and activator / deactivator system.

[0085] In some embodiments, the disclosure provides methods for depolymerizing a polymeric material. In some embodiments, a polymeric material is subjected to mechanical force in the presence of a small molecule chain transfer agent to capture mechanoradicals and generate functionalized polymer chains, and the method further comprises heating the polymeric material at a temperature of less than 400 °C. In other embodiments, a polymeric material is subjected to mechanical force without any added small molecule chain transfer agent, and the resulting mechanically degraded polymer is then heated at a temperature of less than 400 °C.

[0086] In some embodiments, the polymeric material comprises polystyrene, a polyolefin, a poly(meth)acrylate, polyvinyl chloride, polyvinyl acetate, a copolymer thereof, or a blend thereof. In some embodiments, the polymeric material comprises PMMA or another polymethacrylate. In certain embodiments, the small molecule chain transfer agent comprises a trithiocarbonate, a copper halide, a phthalimide, a dithioester, a dithiocarbamate, or a combination thereof.Attorney Docket No. 10975-084W01

[0087] CSURF Ref.: 2024-097 The heating step can be carried out at a temperature of less than 400 °C, such as less than 375 °C, less than 350 °C, less than 325 °C, less than 300 °C, less than 275 °C, or less than 250 °C. In some embodiments, the polymeric material is heated at a temperature in the range of 100 °C to less than 400 °C, 100 °C to less than 350 °C, 100 °C to less than 300 °C, 150 °C to less than 300 °C, 200 °C to less than 300 °C, or 200 °C to less than 275 °C.

[0088] Heating can be conducted under inert atmosphere, reduced pressure, or other conditions suitable to promote evolution and capture of monomer.

[0089] In some embodiments, the polymeric material is heated at the selected depolymerization temperature for a time in a range of 30 minutes to 24 hours. In some embodiments, the heating time is from 1 hour to 18 hours, from 1 hour to 12 hours, from 1 hour to 8 hours, from 2 hours to 12 hours, or from 2 hours to 8 hours. 'The specific time and temperature can be selected to achieve a target degree of depolymerization while balancing energy input and process throughput.

[0090] In some embodiments, the method depolymerizes at least 10% by weight of the polymeric material to an original monomer. In other embodiments, the method depolymerizes at least 15%, at least 20%, at least 25%, at least 30%, at least 40%, at least 45%, or at least 50% by weight of the polymeric material to an original monomer. As used herein, “original monomer” refers to the monomer or monomers from which the polymeric material was originally formed, such as methyl methacrylate in the case of PMMA.

[0091] In one illustrative embodiment, PMMA that has been functionalized with TTC end groups via mechanoradical capture is subjected to bulk heating in a TGA experiment, and the TTC-functionalized PMMA exhibits substantial mass loss and monomer evolution at temperatures significantly lower than pristine PMMA under comparable conditions. In another embodiment, PMMA that has been subjected to ball milling without TTC or other additives exhibits a steady mass loss at lower temperatures than pristine PMMA, consistent with a depolymerization mechanism facilitated by unsaturated chain ends formed during mechanical degradation. Proton NMR spectra of ball-milled PMMA show new resonances consistent with vinylidene chain-end groups, supporting the presence of unsaturated chain ends that promote unzipping depolymerization.

[0092] Although many embodiments are described herein with reference to specific polymers (e.g., polystyrene, PMMA), specific small molecule chain transfer agents (e.g., bis(butyl trithiocarbonate), copper halides, phthalimides), and specific mechanical processes (e.g., ball milling, ultrasonication), the methods are not limited to these particular examples.Attorney Docket No. 10975-084W01

[0093] CSURF Ref.: 2024-097 Mechanoradicals are formed under mechanical force regardless of polymer type, so the approaches described herein can be applied to a wide range of commercially relevant polymers and polymer blends, including but not limited to those explicitly mentioned above.

[0094] In some embodiments, the methods further comprise recovering and purifying monomer from the depolymerization step and using the recovered monomer to prepare new polymeric materials. In other embodiments, the methods further comprise incorporating the repolymerized or depolymerized products into articles of manufacture, such as films, fibers, molded parts, or composite materials.

[0095] In still other embodiments, the disclosure provides systems comprising: (i) a mechanical processing unit configured to apply mechanical force to a polymeric material in the presence of a small molecule chain transfer agent, and (ii) a downstream unit selected from a polymerization reactor for repolymerization and a heating reactor for depolymerization, or a combination thereof. Such systems can be designed to receive polymeric waste streams, perform functionalizing mechanical processing, and direct the resulting functionalized materials to repolymerization or depolymerization pathways as desired.

[0096] A number of embodiments of the disclosure have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

[0097] By way of non-limiting illustration, examples of certain embodiments of the present disclosure are given below. The examples provided in the provisional application illustrate certain non-limiting embodiments of these methods and systems, including specific ball milling conditions, tri thiocarbonate functionalization levels, RAFT chain extension protocols, rheological characterization, and TGA -based depolymerization studies, and demonstrate that functionalization through radical capture during mechanical degradation is possible and can be used to generate high-value materials and monomers from polymeric waste.

[0098] EXAMPLES

[0099] The following examples are set forth below' to illustrate the methods and results according to the disclosed subject matter. These examples are not intended to be inclusive of all aspects of the subject matter disclosed herein, but rather to illustrate representativeAttorney Docket No. 10975-084W01

[0100] CSURF Ref.: 2024-097 methods and results. These examples are not intended to exclude equivalents and variations of the present invention, which are apparent to one skilled in the art.

[0101] Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in °C or is at ambient temperature, and pressure is at or near atmospheric. There are numerous variations and combinations of reaction conditions, e.g., component concentrations, temperatures, pressures, and other reaction ranges and conditions that can be used to optimize the product purity and yield obtained from the described process. Only reasonable and routine experimentation will be required to optimize such process conditions.

[0102] Example 1: Application of chain transfer agents for mechanoradical capture for generation of high value polymers during mechanical recycling.

[0103] Summary

[0104] Plastic consumption has increased drastically in the modern era, inevitably leading to an increase in plastic waste. While recycling was historically proposed to counteract this influx, the combination of the heating and shearing forces innate to this process leads to the formation of highly reactive, short-lived radical species that can induce chain degradation of polymers. This decreases the overall molecular weight of the material, inevitably resulting in lower-value products. This example demonstrates improvements that will increase the mechanical recyclability of polymer waste by introducing accessible functionality to degraded polymers through mechanoradical capture. Trithiocarbonate (TTC) chain transfer agents (CTAs), typically used in reversible addition fragmentation chain transfer (RAFT) polymerizations, have the unique ability to stabilize and capture radicals. Thus, introducing these small molecules during the mechanical recycling process are shown to capture the mechanoradicals formed, effectively functionalizing the waste polymers. These functionalized polymers are then employed as macroinitiators for controlled homo- and copolymerization. In addition, TTC functionalities are used as labile groups that allow for depolymerization to monomer at more accessible temperatures. This novel method generates both higher molecular weight materials akin to virgin polymers and produces monomers that can be repolymerized, offering a promising path toward a circular plastic economy Introduction

[0105] Polymeric materials have become indispensable in modern life and are integral in everyday products from clothing to tires. Largely due to this versatility, plastic waste hasAttorney Docket No. 10975-084W01

[0106] CSURF Ref.: 2024-097 increased almost 300% in the United States over the past 40 years. However, there is a lack of sustainable end-of-life options to counteract this influx, as only 9% of the plastic ever made has been recycled. While the inherent stability of polymeric materials is a desirable property for performance, it hinders the ease of degradation. Hence, landfills become saturated, and waste accumulates. Additionally, because of the poor recycling rate of polymeric materials,2new polymers need to be synthesized, increasing our dependence on the fossil fuels from which most monomers are derived.

[0107] While recycling was historically proposed to minimize plastic waste accumulation, difficulty in plastic sorting, contamination from additives, and chain scission from heating and shearing forces ultimately leads to the downcycling of materials that survive the recycling process. One of the many problems with mechanical recycling is chain degradation resulting from the formation of highly reactive, short-lived radical species that form under mechanical force. These mechanoradicals can lead to chain scission, chain branching, and crosslinking -decreasing overall molecular weight and increasing polydispersity. Because materials properties are highly dependent on molecular weight, these scission events inevitably lead to downcycling to lower value products (Figure 1A).

[0108] It is well established in the field of polymer science that the fracture of polymer chains results in radical formation. While chains fracture under mechanical force the resultant radical species terminate through various pathways. Most often, termination leads to shorter chains; however a variety of chemistries have been used to capture the active radical species before termination. For example, ball milling has been used to fluorescently label polymers through the capture of radicals formed during chain scission. Additionally, low ceiling temperature polymers have been functionalized with phthalimide moieties through mechanoradical capture during ultrasonication (Figure IB). Incorporation of this phthalimide functionality has recently been found to lower ceiling temperatures for depolymerization. Mechanoradical species have also been shown to catalyze reactions. Polyethylene mechanoradicals produced under ball milling have been shown to catalyze the dehalogenation of various small molecules. Alternatively to radical termination and capture pathways, Choi and coworkers has recently shown radical depropagation of polymethacrylates through ball milling. This method achieved up to 40% depolymerization to monomer in the presence of minimal solvent, as well as molecular weights <1 kDa.

[0109] We wondered if we could similarly capture these radicals being formed under mechanical force with small molecule chain transfer agents (CTAs) to enable better reuse andAttorney Docket No. 10975-084W01

[0110] CSURF Ref.: 2024-097 recycling of polymers. We were inspired by the work by Stache and Fors using bis(tliiocarbonyl) disulfide compounds, typically precursors to traditional reversible addition fragmentation atom transfer (RAFT) agents, to capture radicals formed on small molecules and polymers formed from hydrogen atom transfer (HAT) reactions. Specifically, by functionalizing polymers with tri thiocarbonates (TTCs) using radical capture, this work was able to then chain extend and create grafted polymers (Figure IB). In addition, TTCs have been shown to decrease the ceiling temperature for depolymerization. We thus hypothesized that TTCs could similarly capture radicals formed under mechanical force and enable chainextension or decreased ceiling temperatures from “waste” plastics (Figure 1C).

[0111] Previous work using ultrasonication has captured mechanoradicals using either nitroxide species or copper halides to cap polymer chains. Using either functionality, both works were able to chain extend the resulting macroinitiators to form block copolymers (Figure IB). We wondered if we could extend this concept to TTCs using RAFT polymerization that would provide advantages such as a large monomer scope, moderate temperatures, high end group fidelity, as well as a living chain end. Because RAFT agents allow for an equilibrium between active and deactivated chains, they also allow for a living, controlled polymerization. Thus, due to their role of radical stability in RAFT' polymerizations, we hypothesized that TTCs could capture radicals formed under mechanical force.

[0112] While ultrasonication results in narrow dispersities of the resultant degraded polymers, this technique has many limitations. Ultrasonication relies on the formation and subsequent collapse of cavitation bubbles in solution to cause homolytic cleavage of polymer chains. Thus, this technique is severely limited by concentration due to the inherent viscosity of polymers and must be performed in exceedingly dilute solution. Alternati vely, by utilizing ball milling, polymers can be degraded without the use of solvent and in the bulk.

[0113] Herein, we describe the mechanical degradation, radical capture, and repolymerization of poly(methyl methacrylate) (PMMA) and polystyrene (PS) using ultrasonication and ball milling.

[0114] Results and Discussion

[0115] Simulating chain scission. To investigate mechanoradical formation and capture, we employed ultrasonication and ball milling as methods to induce polymer chain scission. PMMA and PS were chosen due to their widespread commercial relevance among radical-derived polymers, making them representative materials for evaluating mechanoradicalAttorney Docket No. 10975-084W01

[0116] CSURF Ref.: 2024-097 capture in plastic recycling. Ultrasonication of 190 kDa PMMA and 150 kDa PS consistently resulted in Mnvalues of approximately 50 kDa and 54 kDa, respectively, with dispersities (D) of ~1.2. In contrast, ball milling led to more extensive degradation, yielding Mnvalues of 5 kDa for PMMA and 12 kDa for PS, with significantly higher dispersities (1.1-4.5). These differences align with the mechanisms of each technique: ultrasonication induces scission predominantly at the midpoint of polymer chains until a limiting molecular weight is reached, resulting in uniform breakage and lower dispersity; whereas ball milling causes more stochastic degradation due to random mechanical impacts, leading to broader molecular weight distributions. Given its ability to achieve greater chain scission, operate under solvent- free conditions, and enable easier scalability (as ultrasonication requires dilute conditions of 5 mg / mL), we selected ball milling as the method for further studies.

[0117] Optimization of ball milling conditions to achieve sufficient chain scission was performed by varying the polymer mass, ball mass, and milling time. Notably, the polymer’s physical texture, including the grain size of the precipitate, influenced degradation efficiency. To minimize variations due to particle size, PS and PMMA were dissolved and reprecipitated before milling. Under these conditions, we observed reproducible chain scission with consistency in molecular weight reduction across experiments.

[0118] Capturing mechanoradicals with TTCs. With consistent chain scission occurring under ball milling conditions, we then added bis(butyl trithiocarbonate) (bisTTC) to capture mechanoradicals being formed during the milling process. However, we found that the addition of > 10 wt% bisTTC significantly suppressed degradation. We hypothesize that this suppression arises from increased material flow and plasticization, reducing localized mechanical stress and shear. Additionally, the presence of bisTTC likely dissipates impact energy, similar to prior studies where liquid-assisted grinding (LAG) significantly reduced polymer degradation.

[0119] To test this hypothesis, we milled PMMA with varying amounts of t-butanol and classified the conditions on the η-scale, which describes the ratio of solvent volume to solute mass. As expected, when the q-value was increased, the molecular weight and dispersity of the resulting milled polymer remained large, indicating inhibition of chain scission events. We found that values greater than ~ η = 0.2, which falls into the range of LAG, significantly inhibited degradation, thereby reducing polymer functionalization with the bisTTC, likely due to a decrease in available mechanoradicals.Attorney Docket No. 10975-084W01

[0120] CSURF Ref.: 2024-097 Keeping rj < 0.2, we varied the amount of bisTTC milled with PS and PMMA and analyzed the samples to see if any TTC was incorporated (Figures 2A-2B, Table 1). Polymers were first purified through multiple precipitations to remove any unreacted T C and analyzed by NMR, size exclusion chromatography (SEC), UV-Vis spectroscopy, and thermal gravimetric analysis coupled with mass spectrometry (TGA-MS). While protons associated with the TTC were visible by ’ ll NMR, due to overlap with protons associated with other chain ends, the degree of functionalization could not be reliably estimated by their relative integration compared to the polymer chain. Similarly, we consistently observed CS2 by TGA-MS, a fragment of the TTC chain end, but could not quantify TTC incorporation. We did find, however, that because TTCs absorb at 310 nm, while PS and PMMA do not, we were able to take advantage of the unique spectroscopic characteristics of the TTC to determine functionalization. In particular, UV / Vis spectroscopy coupled with size exclusion chromatography (SEC-UV) was especially insightful, as it allowed for confirmation that absorption was not due to residual bisTTC small molecules. Furthermore, for bimodal distributions resulting from incomplete degradation, an increase of the UV signal at 310 nm was only present at lower molecular weight, confirming that TTC incorporation only occurs for chains undergoing chain-scission events.

[0121] To quantify the incorporation of TTC into ball milled polymer samples, we made a calibration curve using the SEC-UV absorption data from a model TTC -functional polystyrene derived from the RAFT polymerization of styrene with cyanopropyl butyl tri thiocarbonate. By

[0122]

[0123] NMR, the end-group fidelity of the TTC was > 95%, allowing us to assume ~1 TTC / polymer chain. By comparing the absorption of ball milled samples to the calibration curve, we were able to estimate the mol % TTC incorporated into each samples.

[0124] Table 1.

[0125]

[0126] Attorney Docket No. 10975-084W01

[0127] CSURF Ref.: 2024-097

[0128]

[0129] Repolymerization of TTC-functionalized PS and PMMA. After the successful demonstration of mechanoradical capture during ball milling and ultrasonication of PS and PMMA by TTCs, RAFT' polymerizations were then performed to chain extend the degraded polymers. Various control experiments were performed on both model polymers with known TTC end groups and degraded polymers that were unfunctionalized to demonstrate that chain extension could occur but only in the presence of a TTC end group. Blue light polymerizations were used to mitigate the need for an exogenous initiator. Excitingly, the degraded macroinitators were successfully chain-extended to target their original molecular' weights before mechanical degradation as demonstrated in Figure 4A.

[0130] To test the chain-extended macroinitiator properties, we scaled up the ball milling reactions. While this resulted in a smaller reduction in molecular weight, the polymer still degraded significantly, and similar TTC incorporations were observed. In addition, tensile testing of the chain extended polymers showed the restoration of their original mechanical properties.

[0131] We also hypothesized that the addition of monomer could increase the lifetime of radicals formed (through propagation of the radical), thereby increasing the potential for TTCs to add to the fragmented chain. In addition, this could aid in limiting the formation of primary radicals that when captured by TTC, which would not be able to chain extend. Using optimized volumes of monomer (r| = 0.075), degradation was comparable to when milling with just TTC. TTC incorporation was on average 0.4 wt% with and without monomer present during ball milling for PS. While overall TTC incorporation decreased, the proportion of active TTC chain ends increased as demonstrated by subsequent chain extensions.

[0132] Mechanical Testing. To evaluate the mechanical impact of degradation and subsequent repolymerization, we performed temperature-sweep oscillatory shear rheology on PMMA samples before ball milling (pristine), after ball milling, and after RAFT-based chain extension. The pristine polymer exhibits a well-defined rubbery plateau above the glass transition temperature (Tg » 100 °C), consistent with a high molecular weight, entangled network. In contrast, the ball-milled polymer shows a reduced Tg and no observable rubbery plateau, indicative of a loss in entanglement. This behavior is expected, as the molecular weight of the ball-milled samples falls below the entanglement threshold for PMMA (Me, 16,000 g / mol), with measured Mnvalues below 10,000 g / mol. These results confirm thatAttorney Docket No. 10975-084W01

[0133] CSURF Ref.: 2024-097 chain scission during ball milling significantly compromises the mechanical integrity of the material. See Figure 5.

[0134] Depolymerization of Functionalized PMMA. Inspired by recent studies demonstrating that trithiocarbonate (TTC) end groups can lower the ceiling temperature of poly(methyl methacrylate) (PMMA), we hypothesized that functionalizing PMMA with TTC via mechanoradical capture would enable depolymerization to monomer at reduced temperatures. However, in the course of these experiments, we discovered that PMMA subjected to ball milling — even in the absence of TTC or other additives — exhibited significantly enhanced depolymerization under thermal conditions.

[0135] As shown in Figure 3, thermogravimetric analysis (TGA) revealed that ball-milled PMMA begins to lose mass at much lower temperatures than pristine PMMA, with a steady degradation profile suggestive of depolymerization rather than random scission. We hypothesized that this behavior may arise from the formation of unsaturated chain ends generated during ball milling. Specifically, if the mechanoradicals formed during milling undergo disproportionation rather than recombination, they can yield vinyl-terminated chain ends that are known to facilitate unzipping depolymerization.

[0136] To test this hypothesis, we analyzed the ball -milled PMMA by proton NMR and observed new resonances consistent with unsaturated chain-end groups, supporting the presence of vinylidene moieties. These results suggest that mechanical degradation alone can prime PMMA for depolymerization by introducing reactive chain-end structures, independent of TT’C functionalization.

[0137] Conclusion

[0138] These preliminary results demonstrate that functionalization through radical capture during mechanical degradation is possible. We achieved -0.4 wt% functionalization of both PS and PMMA with ball milling in the presence of 10 wt% TTC. This is an efficient and controlled method of introducing functionality to waste polymers. Importantly, we were able to show controlled chain extension by RAFT homopolymerization and copolymerization to achieve targeted molecular weights and restore mechanical properties of the degraded material. Additionally, we showed that functionalization of PMMA with TTCs through mechanoradical capture allowed bulk depolymerization at lower temperatures. We expect that this method can be expanded to other commercial polymers and may serve as a viable route to upcycling plastic waste.

[0139] Materials and MethodsAttorney Docket No. 10975-084W01

[0140] CSURF Ref.: 2024-097 General Reagent Information. Methyl methacrylate (MMA) (99%, Sigma Aldrich) and styrene (99%, Oakwood Chemical) were filtered through a plug of aluminum oxide (activated, neutral, Brockmann I, Sigma Aldrich) to remove inhibitors before use. All other reagents were obtained from Sigma Aldrich, ThermoFisher, Acros Organics, and VWR and used as received. Polystyrene (PS) (Mw= 280,000) and poly(methyl methacrylate) (PMMA) (Mw= 350,000) were purchased from Sigma Aldrich. Sodium hydride (67-63% oil dispersion, Thermo Scientific), carbon disulfide (99.9%, Acros Organics), butanethiol (≥99%, ThermoScientific), iodine (99.5%, Sigma Aldrich), and were used as received.

[0141] Azobisisobutyronitrile (AIBN) (98%, Sigma Aldrich) was recrystallized from methanol before use. Polymerizations were carried out under irradiation with blue LED light (Creative Lighting Solutions, 14.4 W / m, 12 V, wavelength / Hz).

[0142] Instrumentation

[0143] Nuclear Magnetic Resonance (NMR) Spectroscopy. 'H NMR spectra were acquired at room temperature on a Bruker US 400 (400 MHz) NMR instrument. The chemical shifts of peaks in the NMR spectra were referenced to the residual solvent peak (7.26 ppm and 2.50 ppm for CDCl₃ and d-DMSO respectively). Data was analyzed using MestreNova software.

[0144] Size Exclusion Chromatography (SEC). SEC chromatograms were acquired at room temperature on an Agilent 1260 Infinity II LC using a 50 μm PL Gel column at ambient temperature, in line with a Wyatt Technologies DAWN 8 light scattering detector, Optilab refractive index detector, and UV absorbance detector. All chromatograms were acquired in DMF and UV absorbance was recorded at 310 or 330 nm.

[0145] UV-Visible Spectroscopy. UV / Vis spectra were acquired at room temperature on a Cary 3500 Multicell UV-Vis Spectrophotometer. Scans were acquired from 200.00-800.00 nm with an averaging time of 0.020 s.

[0146] Thermogravimetric Analysis (TGA). TGA experiments were performed on a TA TGA-55 analyzer coupled with an electrospray ionization mass spectrometer.

[0147] Synthesis of ReagentsAttorney Docket No. 10975-084W01

[0148] CSURF Ref.: 2024-097 Bis(butyl trithiocarbonate)

[0149]

[0150] Bis(butyl trithiocarbonate) (bis(TTC)) was synthesized according to a previous procedure.1Sodium hydride (60% in mineral oil, 0.417 g, 10.4 mmol, 1.04 equiv.) was added to a flame-dried 50 mL Schlenk flask along with t-butyl methyl ether (7.0 ml, 1.4 M). The flask was cooled to 0 °C in an ice bath under N2. Butanethiol (1.1 mL, 10.0 mmol, 1.0 equiv.) was added to the flask dropwise. The reaction mixture was allowed to slowly come to room temperature and stirred for an additional 3 hours under N₂. The flask was then cooled back to 0 °C in an ice bath. Carbon disulfide (0.63 mL, 10.4 mmol, 1.04 equiv.) was subsequently added dropwise. The reaction was allowed to warm to room temperature and was stirred for another 3 hours under N₂. Pentane (25 ml) was then added to the reaction mixture, resulting in precipitation of the desired yellow solid, which was isolated by filtration and washed with additional pentane. The solid was redissolved in diethyl ether (15 ml) and transferred to a 50 ml round bottom flask. This flask was cooled to 0 °C in an ice bath under N2. Solid iodine (1.5 g, 5.5 mmol, 0.55 equiv.) was added over the course of 5 minutes. The reaction was allowed to stir overnight under N2. The the solid white Nal salt was removed via filtration. The orange filtrate was extracted with deionized water (20 mL), saturated aqueous sodium thiosulfate (3 x 20 mL), and brine (20 mL). The resultant organic solution was dried over MgSO₄, filtered, and concentrated in vacuo to produce a bright orange oil. Yield: 93.5%. ¹H NMR assignments were consistent with previously reported spectra. ¹H NMR (400 MHz, CDCl₃) δ = 3.31 (t, 4H), 1.69 (p, 4H), 1.42 (s, 4H), 0.93 (t, 6H)

[0151] Cyanopropyl butyltrithiocarbonate

[0152]

[0153] Cyanopropyl butyltrithiocarbonate was synthesized according to a prior procedure.2In a 3-neck round bottom flask equipped with reflux condenser and connected to oil bubbler, bis(butyl trithiocarbonate) (0.4237 g, 1.274 mmol, 1 eq.) was dissolved in ethyl acetate (100 mL) withAttorney Docket No. 10975-084W01

[0154] CSURF Ref.: 2024-097 AIBN (0.3138 g, 1.911 mmol, 1.5 eq.) and purged with N2 for 30 minutes. After purging, the solution was heated to 70 °C and stirred for 72 hours. This solution was reduced via rotary evaporation and purified by column chromatography two sequential times using a gradient solvent system (silica gel, 100% hexanes until first colored band elutes, 90:10 hexanes:ethyl acetate to elute second colored band containing product). The product fractions were combined and reduced via rotary evaporation followed by drying in vacuo to yield the product as red-orange oil.1H NMR assignments were consistent with previously reported spectra.

[0155]

[0156] NMR (400 MHz, CDCl₃) δ = 3.33 (t, 2H), 1.86 (s, 6H), 1.67 (p, 2H), 1.41 (m, 2H), 0.93 (t, 3H)

[0157] Model Polystyrene-TTC

[0158]

[0159] In a 25 mL Schlenk flask, styrene (10.42 g, 100 mmol, 100 equiv.), azobisisobutyronitrile (32 mg, 0.2 mmol, 0.2 equiv.), cyanopropyl butyl trithiocarbonate (2) (233 mg, 1 mmol, 1 equiv.) were dissolved. The reaction mixture was degassed with nitrogen for 10 minutes. The flask was then heated at 110 °C for 6 hours. The reaction was cooled to room temperature and precipitated three times into methanol and filtered to give a yellow powder. The precipitate was dried under vacuum at 45 °C overnight. Mn= 5700 Da. Mw= 5800 Da. D = 1.02.

[0160] Poly(methyl methacrylate)-TTC

[0161]

[0162] In a 25 mL Schlenk flask, methyl methacrylate (3.006 g, 30.03 mmol, 130 equiv.), azobisisobutyronitrile (16 mg, 0.096 mmol, 0.1 equiv.), cyanopropyl butyl trithiocarbonate (2) (54.4 mg, 0.233 mmol, 1 equiv.) were dissolved in 1,4-dioxane (2 mL). The reaction mixture was degassed with nitrogen for 10 minutes. The flask was then heated at 75 °C for 3 hours. To purify, the reaction mixture was precipitated three times into methanol and filtered. The product was a yellow powder. The precipitate was dried under vacuum at 45 °C overnight. Mn= 15.3 kDa. Mw= 16.0 kDa. D = 1.04.

[0163] General Procedure for Ultrasonication ExperimentsAttorney Docket No. 10975-084W01

[0164] CSURF Ref.: 2024-097 A circulating pump was assembled to ensure constant temperature of the ultrasonicated solution. A 5 mg mL⁻¹ solution of PMMA (Mn= 190 kDa, D = 1.75) or PS (Mn = 150 kDa, D = 1.90) was prepared in HPLC grade DMF. The probe tip was placed ca. 0.75 in into the solution to prevent frothing. The solution was sonicated at 100% amplitude and 20 kHz for 60 min, with the on / off pulse set to 30 seconds on and 30 seconds off. To purify, the reaction mixture was precipitated three times into methanol and filtered. The precipitate was dried under vacuum at 45 °C overnight.

[0165] General Procedure for Ball Milling Experiments

[0166] PS (Mn= 150 kDa, D = 1.90, 500 mg) or PMMA (Mn= 190 kDa, D = 1.75, 500 mg) was added to a stainless-steel or ceramic ball milling jar respectively with 35 g of the corresponding 5 mm balls. The samples were ball milled for 1 hour at 1160 rpm to produce a white powder.

[0167] General Procedure for Photoinitiated Chain Extension

[0168] Polystyrene

[0169]

[0170] Styrene (1.309 g, 12.5 mmol, 5000 equiv.) and ball milled PS (Mn= 40 kDa, 102 mg, 0.0025 mmol, 1 equiv.) were dissolved in a Schlenk flask. The reaction mixture was degassed with nitrogen for 10 minutes. The flask was irradiated in a blue light photoreactor for 24 hours at room temperature. To purify, the reaction mixture was precipitated three times into methanol and filtered. The product was a white powder. The precipitate was dried under vacuum at 45 °C overnight. Conversion: 30%; Mn: 160 kDa; Đ = 1.925.

[0171] Chain extension of PS milled with TTC:

[0172] entry polymer

[0173]

[0174]

[0175] 1 280 kDa PS 150 280 1.9

[0176] 2 Milled with TTC 41 76 1.83

[0177] 3 Chain Extended 160 307 1.93Attorney Docket No. 10975-084W01 CSURF Ref.: 2024-097 General Procedure for Photoinitiated Chain Extension of Poly(m ethyl methacrylate)

[0178] Poly(methyl methacrylate)

[0179]

[0180] Methyl methacrylate (1.031 g, 10.3 mmol, 2500 equiv.) and ball milled

[0181] PMMA (Mn=24.3 kDa, 100 mg, 0.0041 mmol, 1 equiv.) were dissolved in 1,4-dioxane (1 mL) in a Schlenk flask. The reaction mixture was degassed with nitrogen

[0182] for 10 minutes. The flask was irradiated in a blue light photoreactor for 3 hours at

[0183] room temperature. To purify, the reaction mixture was precipitated three times into methanol and filtered. The product was a white powder. The precipitate was dried

[0184] under vacuum at 45 °C overnight. Conversion: 90%; Mn: 248.1 kDa; D =1.28.

[0185] General Procedure for Photoinitiated Chain Extension of Polystyrene

[0186] with Methyl Methacrylate

[0187] Poly(styrene-co-methyl methacrylate)

[0188]

[0189] In a Schlenk flask, methyl methacrylate (0.523 g, 5.0 mmol) and ball milled PS (Mn= 40 kDa, 49.5 mg, 0.001 mmol) were dissolved in 0.74 mL of 1,4-dioxane. The reaction mixture was degassed with nitrogen for 10 minutes. The flask was irradiated in a blue light photoreactor for 24 hours at room temperature. To purify, the reaction mixture was precipitated three times into methanol and filtered. The product was a white powder. The precipitate was dried under vacuum at 45 °C overnight. Mn: 50 kDa; D = 1.942.

[0190] General Procedure for Photoinitiated Chain Extension of Poly(methyl methacrylate) with Styrene (producing Poly(styrene-co-methyl methacrylate))

[0191] In a Schlenk flask, styrene and ball milled PMMA were dissolved in 1,4-dioxane. The reaction mixture was degassed with nitrogen for 10 minutes. The flask was irradiated in a blue light photoreactor at room temperature. To purify, the reaction mixture was precipitatedAttorney Docket No. 10975-084W01

[0192] CSURF Ref.: 2024-097 three times into methanol and filtered. The product was a white powder. The precipitate was dried under vacuum at 45 °C overnight.

[0193] References

[0194] (1) The Real Truth About the U. S. Plastics Recycling Rate,' Bennington,

[0195] (2) OECD. Global Plastics Outlook: Economic Drivers, Environmental Impacts and Policy Options,' OECD, 2022. https: / / doi.org / 10.1787 / de747aef-en.

[0196] (3) Raliimi, A.; Garcia, J. M. Chemical Recycling of Waste Plastics for New Materials Production. Nat. Rev. Chem. 2017, 1 (6), 1-11. https: / / doi.org / 10.1038 / s41570-017-0046. (4) Li, H.; Aguirre -Villegas, H. A.; Allen, R. D.; Bai, X.; Benson, C. H.; Beckham, G. T.; Bradshaw, S. L.; Brown, J. L.; Brown, R. C.; Cecon, V. S.: Curley, J. B.; Curtzwiler, G. W.; Dong, S.; Gaddameedi, S.; Garcia, J. E.; Hermans, I.; Kim, M, S.; Ma, J.; Mark, L. O.;

[0197] Mavrikakis, M.; Olafasakin, O. O.; Osswald, T. A.; Papanikolaou, K. G.; Radhakrishnan, H.; Sanchez Castillo, M. A.; Sanchez-Rivera, K. L.; Tumu, K. N.; Van Lehn, R. C.: Vorst, K. L.; Wright, M. M,; Wu, J.; Zavala, V, M.; Zhou, P.; Huber, G. W. Expanding Plastics Recycling Technologies: Chemical Aspects, Technology Status and Challenges. Green Chem. 2022, 24 (23), 8899-9002. https: / / doi.org / 10.1039 / D2GC02588D.

[0198] (5) Schyns, Z. O. G.; Shaver, M, P, Mechanical Recycling of Packaging Plastics: A Review. Macromol. Rapid Commun. 2021, 42 (3), 2000415.

[0199] https: / / doi.org / 10.1002 / marc.202000415.

[0200] (6) Kauzmann, W.; Eyring, H. lire Viscous Flow of Large Molecules. J. Am. Chem. Soc.

[0201] 1940, 62 (11), 3113-3125. https: / / doi.org / 10.1021 / ja01868a059.

[0202] (7) Staudinger, H.; Bondy, H. F. Uber Isopren Und Kautschuk, 19. Mitteil.: Uber Die MolekiilgrbBe Des Kautschuks Und Der Balata. Berichte Disch. Chem. Ges. B Ser. 1930, 63 (3), 734-736. https: / / doi.org / 10.1002 / cber.19300630330.

[0203] (8) Staudinger, H.; Leupold, E. O. Uber Isopren Und Kautschuk, 18. Mitteil.: Viscositats-Untersuchungen an Balata. Berichte Disch. Chem. Ges. B Ser. 1930, 63 (3), 730-733. https: / / doi.org / 10.1002 / cber.19300630329.

[0204] (9) Staudinger, H.; Heuer, W. Uber Hochpolymere Verbindungen, 93. Mitteil.: Uber Das ZerreiBen Der Faden-Molekiile Des Poly-styrols. Berichte Dtsch. Chem. Ges. B Ser. 1934, 67 (7), 1159-1164. https: / / doi.org / 10.1002 / cber.19340670708.

[0205] (10) Pike, M,; Watson, W. F. Mastication of Rubber, I. Mechanism of Plasticizing by Cold Mastication. J. Polym. Sci. 1952, 9 (3), 229-251.

[0206] https: / / doi.org / 10.1002 / pol.1952.12009030.Attorney Docket No. 10975-084W01

[0207] CSURF Ref.: 2024-097 (11) Kuzuya, M,; Kondo, S.; Noguchi, A.; Noda, N. Nature of Mechanoradical Formation and Reactivity with Oxygen in Methacrylic Vinyl Polymers. J. Polym. Sci. Part B Polym. Phys. 1992, 30 (1), 97-103. https: / / doi.org / 10.1002 / polb.1992.090300110.

[0208] (12) Kubota, K.; Toyoshima, N.: Miura, D.; Jiang, J.; Maeda, S.; Jin, M.: Ito, H.

[0209] Introduction of a Luminophore into Generic Polymers via Mechanoradical Coupling with a Prefluorescent Reagent. Angew. Chem. Int. Ed. 2021, 60 (29), 16003-16008. https: / / doi.org / 10.1002 / anie.202105381.

[0210] (13) Young, J. B.; Goodrich, S. L.; Lovely, J. A.; Ross, M. E.; Bowman, J. I.; Hughes, R. W.; Sumerlin, B. S. Mechanochemically Promoted Functionalization of Postconsumer Poly(Methyl Methacrylate) and Poly(a-Methylstyrene) for Bulk Depolymerization. Angew. Chem. Int. Ed. 2024, e202408592. https: / / doi.org / 10.1002 / anie.202408592.

[0211] (14) Young, J. B. Hughes, R. W.; Tamura, A. M.; Bailey, L. S.; Stewart, K. A.; Sumerlin, B. S. Bulk Depolymerization of Poly(Methyl Methacrylate) via Chain-End Initiation for Catalyst-Free Reversion to Monomer. Chem 2023. https: / / doi.org / 10.1016 / j.chempr.2023.07.004.

[0212] (15) Kubota, K.; Jiang, J.; Kamakura, Y.; Hisazumi, R.; Endo, T.; Miura, D.; Kubo, S.: Maeda, S,; Ito, H. Using Mechanochemistry to Activate Commodity Plastics as Initiators for Radical Chain Reactions of Small Organic Molecules. J. Am. Chem. Soc. 2023. https: / / doi.org / 10.1021 / jacs.3c12049.

[0213] (16) Jung, E.; Cho, M.; Peterson, G. I.; Choi, T.-L. Depolymerization of Polymethacrylates with Ball-Mill Grinding. Macromolecules 2024. https: / / doi.org / 10.1021 / acs.macromol.3c02664.

[0214] (17) Stache, E. E.: Kottisch, V.; Fors, B. P. Photocontrolled Radical Polymerization from Hydridic C-H Bonds. J. Am. Chem. Soc. 2020, 142 (10), 4581-4585.

[0215] https: / / doi.org / 10.1021 / jacs.0c00287.

[0216] (18) Whitfield, R.; Jones, G. R.; Truong, Nghia. P.; Manring, L. E.; Anastasaki, A.

[0217] Solvent-Free Chemical Recycling of Polymethacrylates Made by ATRP and RAFT Polymerization: High-Yielding Depolymerization at Low Temperatures. Angew. Chem. 2023, 135 (38), e202309116. https: / / doi.org / 10.1002 / ange.202309116.

[0218] (19) Bartsch, M.; Schmidt-Naake, G. Application of Nitroxide-Terminated Polymers Prepared by Sonochemical Degradation in the Synthesis of Block Copolymers. Macromol. Chem. Phys. 2006, 207 (2), 209-215. https: / / doi.org / 10.1002 / macp.200500380.Attorney Docket No. 10975-084W01

[0219] CSURF Ref.: 2024-097 (20) Degirmenci, M.; Catalgil-Giz, H.; Yagci, Y. Synthesis of Block Copolymers by Combined Ultrasonic Irradiation and Reverse Atom Transfer Radical Polymerization Processes. J. Polym. Sci. Part Polym. Chem. 2004, 42 (3), 534-540.

[0220] https: / / doi.org / 10.1002 / pola.10879.

[0221] (21) Kerr, A.; Moriceau, G.; Przybyla, M. A.; Smith, T.; Perrier, S. Bis(Trithiocarbonate) Disulfides: From Chain Transfer Agent Precursors to Iniferter Control Agents in RAFT Polymerization. Macromolecules 2021, 54 (14), 6649-6661. https: / / doi.org / 10.1021 / acs.macromol.1c00565.

[0222] (22) Cravotto, G.; Cintas, P. Harnessing Mechanochemical Effects with Ultrasound- Induced Reactions. Chem Sci 2012, 3 (2), 295-307. https: / / doi.org / 10.1039 / ClSC00740H. (23) Peterson, G. I.; Ko, W.; Hwang, Y.-J.; Choi, T.-L. Mechanochemical Degradation of Amorphous Polymers with Ball-Mill Grinding: Influence of the Glass Transition Temperature. Macromolecules 2020, 53 (18), 7795-7802.

[0223] https: / / doi.org / 10.1021 / acs.macromol.0c01510.

[0224] (24) Do, J.-L.; Friščić, T. Mechanochemistry: A Force of Synthesis. ACS Cent. Sci. 2017, 3 (1), 13—19. https: / / doi.org / 10.1021 / acscentsci.6b00277

[0225] Other advantages which are obvious, and which are inherent to the invention, will be evident to one skilled in the art. It will be understood that certain features and sub¬ combinations are of utility and may be employed without reference to other features and sub¬ combinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Claims

Attorney Docket No. 10975-084W01CSURF Ref.: 2024-097 CLAIMSWHAT IS CLAIMED IS:

1. A method for recycling a polymeric material, the method comprising:applying a mechanical force to the polymeric material to induce mechanoradical formation in the presence of a small molecule chain transfer agent, thereby capturing mechanoradicals formed by the applied mechanical force.

2. The method of claim 1, further comprising repolymerizing the polymeric material.

3. The method of claim 2, wherein repolymerizing the polymeric material comprising contacting the polymeric material with a radically polymerizable monomer under conditions effective to polymerize the radically polymerizable monomer with the polymeric material.

4. The method of claim 1, further comprising heating the polymeric material at a temperature of less than 400°C (e.g., less than 375°C, less than 350°C, less than 325 °C, less than 300°C, less than 275°C, or less than 250°C), such as a temperature of from 100°C to less than 400°C, from 100°C to less than 375°C, from 100°C to less than 350°C, from 100°C to less than 325°C, from 100°C to less than 300°C, from 100°C to less than 275°C, from 100°C to less than 250°C, from 150°C to less than 400°C, from 150°C to less than 375°C, from 150°C to less than 350°C, from 150°C to less than 325°C, horn 150°C to less than 300°C, from 150°C to less than 275°C, from 150°C to less than 250°C, from 200°C to less than 400°C, from 200°C to less than 375°C, from 200°C to less than 350°C, from 200°C to less than 325°C, from 200°C to less than 300°C, from 200°C to less than 275°C, or horn 200°C to less than 250°C.

5. The method of claim 4, wherein the polymeric material is heated at the temperature for a period of time of from 30 minutes to 24 hours, such as from 1 hour to 18 hours, from 1 hour to 12 hours, from 1 hour to 8 hours, from 2 hours to 18 hours, from 2 hours to 12 hours, or from 2 hours to 8 hours.

6. The method of any one of claims 4-5, wherein the method depolymerizes at least 10% by weight (e.g., at least 15% by weight, at least 20% by weight, at least 25% by weight, atAttorney Docket No. 10975-084W01CSURF Ref.: 2024-097 least 30% by weight, at least 40% by weight, at least 45% by weight, or at least 50% by weight) of the polymeric material to its original monomer.

7. The method of any one of claims 1 -6, wherein the method is performed as a solvent free process (e.g., a process that includes less than 5% by weight solvent, less than 2.5% by¬ weight solvent, less than 1% by weight solvent, less than 0.5% by weight solvent, or less than 0.1% by weight solvent).

8. The method of any one of claims 1-7, wherein the polymeric material comprises polystyrene, a polyolefin, a poly(meth)acrylate, polyvinyl chloride, polyvinyl acetate, a copolymer thereof, or a blend thereof.

9. The method of any one of claims 1-8, wherein the polymeric material comprises polystyrene or poly (methyl methacrylate) (PMMA).

10. The method of any one of claims 1-9, wherein applying the mechanical force comprises ball milling the polymeric material.

11. The method of any one of claims 1-9, wherein applying the mechanical force comprises ultrasonication of the polymeric material.

12. The method of any one of claims 1-11, wherein the small molecule chain transfer agent has a molecular weight of less than 1000 Da, such as less than 800 Da, or less than 500 Da.

13. The method of any one of claims 1-12, wherein the small molecule chain transfer agent comprises a trithiocarbonate, such as bis(butyl trithiocarbonate), Bis[4-(allyloxycarbonyl)benzyl] Trithiocarbonate, S, S-Dibenzyl trithiocarbonate, cyanopropyl butyltrithiocarbonate, or a combination thereof.

14. The method of any one of claims 1-13, wherein the small molecule chain transfer agent comprises a copper halide, a phthalimide, a dithioester, a dithiocarbamate, or a combination thereof.Attorney Docket No. 10975-084W01CSURF Ref.: 2024-09715. A method of depolymerizing a polymeric material, the method comprising:applying a mechanical force to the polymeric material to induce mechanoradical formation in the presence of a small molecule chain transfer agent, thereby capturing mechanoradicals formed by the applied mechanical force; andheating the polymeric material at a temperature of less than 400°C.

16. The method of claim 15, wherein the method comprises heating the polymeric material at a temperature of less than 375°C (e.g., less than 350°C, less than 325°C, less than 300°C, less than 275°C, or less than 250°C), such as a temperature of from 100°C to less than 400°C, from 100°C to less than 375°C, from 100°C to less than 350°C, from 100°C to less than 325°C, from 100°C to less than 300°C, from 100°C to less than 275°C, from 100°C to less than 250°C, from 150°C to less than 400°C, from 150°C to less than 375°C, from 150°C to less than 350°C, from 150°C to less than 325°C, from 150°C to less than 300°C, from 150°C to less than 275°C, from 150°C to less than 250°C, from 200°C to less than 400°C, from 200°C to less than 375°C, from 200°C to less than 350°C, from 200°C to less than 325 °C, from 200°C to less than 300°C, from 200°C to less than 275°C, or from 200°C to less than 250°C.

17. The method of any one of claims 15-16, wherein the polymeric material is heated at the temperature for a period of time of from 30 minutes to 24 hours, such as from 1 hour to 18 hours, from 1 hour to 12 hours, from 1 hour to 8 hours, from 2 hours to 18 hours, from 2 hours to 12 hours, or from 2 hours to 8 hours.

18. The method of any one of claims 15-17, wherein the method depolymerizes at least 10% by weight (e.g., at least 15% by weight, at least 20% by weight, at least 25%’ by weight, at least 30% by weight, at least 40% by weight, at least 45% by weight, or at least 50% by weight) of the polymeric material to its original monomer.

19. The method of any one of claims 15-18, wherein the method is performed as a solvent free process (e.g., a process that includes less than 5% by weight solvent, less than 2.5% by weight solvent, less than 1% by weight solvent, less than 0.5% by weight solvent, or less than 0.1% by weight solvent).Attorney Docket No. 10975-084W01CSURF Ref.: 2024-09720. The method of any one of claims 15-19, wherein the polymeric material comprises polystyrene, a polyolefin, a poly(meth)acrylate, polyvinyl chloride, polyvinyl acetate, a copolymer thereof, or a blend thereof.

21. The method of any one of claims 15-20, wherein the polymeric material comprises polystyrene or poly (methyl methacrylate) (PMMA).

22. The method of any one of claims 15-21, wherein applying the mechanical force comprises ball milling the polymeric material.

23. The method of any one of claims 15-21, wherein applying the mechanical force comprises ultrasonication of the polymeric material.

24. The method of any one of claims 15-23, wherein the small molecule chain transfer agent has a molecular weight of less than 1000 Da, such as less than 800 Da, or less than 500 Da.

25. The method of any one of claims 15-24, wherein the small molecule chain transfer agent comprises a trithiocarbonate, such as bis(butyl trithiocarbonate), Bis[4-(allyloxycarbonyl)benzyl] Trithiocarbonate, S, S-Dibenzyl trithiocarbonate, cyanopropyl butyltrithiocarbonate, or a combination thereof.

26. The method of any one of claims 15-25, wherein the small molecule chain transfer agent comprises a copper halide, a phthalimide, a dithioester, a dithiocarbamate, or a combination thereof.

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