Method for regulating and controlling chiral structure and chiral transfer of triblock copolymer by middle block, chiral triblock copolymer and application of chiral triblock copolymer

Abstract

The invention belongs to the technical field of high polymer materials, and discloses a method for regulating and controlling a chiral structure and chiral transfer of a triblock copolymer by a middle block, the chiral triblock copolymer and application. The method comprises the steps that firstly, a chiral triblock copolymer is selected, the structural general formula of the triblock copolymer is PS-b-B-b-PLLA, B is a middle block, and B is selected from one of the following polymer chain segments: PLA, PEO, PCL, P4VP, P4CS and PMMA; then regulating and controlling the self-assembly behavior of the triblock copolymer through B, so that the copolymer is self-assembled to form a chiral structure or an achiral structure; the regulation comprises the steps of 1) determining chi between the middle block B and the PLLA, and 2) determining the chain length of the middle block B. According to the chiral triblock copolymer, chiral transmission of the triblock copolymer is realized, and a chiral spiral phase structure is formed through self-assembly, and the chiral triblock copolymer is used for preparing advanced functional materials such as chiral photonic crystals, circular polarization luminescent materials and chiral separation membranes.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a method for regulating the chiral structure and chiral transfer of chiral triblock copolymers by medium block copolymers, and the application of chiral triblock copolymers and chiral transfer. Background Technology

[0002] Chirality is ubiquitous in nature, and transferring molecular-level chirality to macroscopic helical superstructures through self-assembly (i.e., chiral transfer) is an important means of preparing advanced functional materials. Block copolymers, due to their inherent microphase separation capabilities, are ideal platforms for achieving chiral transfer.

[0003] Current research mainly focuses on chiral diblock copolymer systems (such as PS-b-PLLA, where b represents a block). In these systems, chiral interactions drive the twisting and movement of microphase separation domains, forming a helical phase (H* phase, where H* represents a chiral helical phase). However, the diblock structure is relatively simple, and the controllability of chiral transfer is limited.

[0004] Triblock copolymers (ABC type) introduce a third block (middle block), theoretically providing a new interface and interaction dimension for the regulation of chiral transfer. However, current research on chiral triblock copolymers is very limited, and most studies focus on chemically similar block combinations (such as PS-PLLA-PLA), whose behavior is closer to that of diblock systems. A key unresolved scientific problem and technological gap is how to precisely regulate the process of "transdomain chiral transfer" by introducing a chemically distinct, achiral middle block, that is, to control the transfer of chirality from the chiral block (such as PLLA) across the achiral middle block to the entire supramolecular assembly, thereby achieving on-demand customization of the final self-assembled nanostructure (chiral or achiral). Summary of the Invention

[0005] To overcome the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for regulating the chiral structure and chiral transfer of triblock copolymers via a mid-block segment. The general formula of the triblock copolymer of this invention is AbBbC*, where A is a polystyrene (PS) segment, C* is a chiral poly(L-lactic acid) (PLLA) segment, and B is a non-chiral mid-block. This invention achieves this by controlling the compatibility between the mid-block and the chiral terminal block (expressed as the Flory-Huggins interaction parameter χ). 中嵌段 / PLLA By measuring the length of the intermediate block and the final self-assembled nanostructure (chiral helical structure or achiral columnar structure) of chiral triblock copolymers, the mechanism of chiral transfer across domains can be controlled and revealed.

[0006] Another object of the present invention is to provide a chiral triblock copolymer. The chiral triblock copolymer has the general structural formula AbBbC*, where A is a polystyrene (PS) segment, C* is a chiral poly-L-lactic acid (PLLA) segment, B is a non-chiral mesoblock, and b represents the block connection symbol, determined by the Flory-Huggins interaction parameter χ. B / PLLA Furthermore, by controlling the domain thickness of the middle block B, transdomain chiral transfer of chiral triblock copolymers can be achieved.

[0007] Another object of the present invention is to provide the application of the above-mentioned triblock copolymer in chiral transfer. The present invention modulates the chemical structure of the middle block B (thereby controlling χ). B / C* By controlling the molecular chain length and the "switch" of transdomain chiral transfer, it is possible to control the fabrication of helical nanostructures or achiral columnar structures.

[0008] The objective of this invention is achieved through the following technical solution: A method for regulating the chiral structure and chiral transfer of a triblock copolymer by a medium block copolymer includes the following steps: First, a triblock copolymer is selected. The general structural formula of the triblock copolymer is PS-bBb-PLLA, where B is a medium block copolymer, and B is selected from one of the following polymer segments: poly(D,L-lactic acid) (PLA), polyethylene oxide (PEO), polycaprolactone (PCL), poly(4-vinylpyridine) (P4VP), poly(4-chlorostyrene) (P4CS), and polymethyl methacrylate (PMMA). Then, the self-assembly behavior of the triblock copolymer is regulated by the middle block B, so that the copolymer self-assembles into a chiral or achiral structure; The specific regulation involves: 1) determining the Flory-Huggins interaction parameter (χ²) between the mid-block B and the chiral terminal block PLLA. B / PLLA ) ; When χ < 0.2, there is a possibility of cross-domain chiral transmission; in this case, B can be PLA, PEO, or PCL. When χ>0.2, transdomain chiral transmission is suppressed, and self-assembly forms achiral structures; at this time, B is P4VP, P4CS, or PMMA. 2) When B is a PLA, PEO, or PCL segment, determine the chain length of the middle segment B; B represents PLA or PEO. When the domain thickness of the B block is less than 10 nm, it self-assembles to form a helical phase, i.e., a chiral structure. When the thickness exceeds 10 nm, chiral transmission is blocked, and it self-assembles to form a non-chiral columnar phase. B is a PCL segment. When the domain thickness of the B segment is ≤7.2 nm, it self-assembles to form a helical phase, i.e., a chiral structure. When the thickness is ≥7.6 nm, chiral transmission is blocked, and it self-assembles to form a non-chiral columnar phase.

[0009] The domain thickness of the B-block is L × N 2 / 3 , where L is the repeating unit length of the middle block B, in nm; N is the degree of polymerization of the middle block B.

[0010] A chiral triblock copolymer with the general structural formula PS-bBb-PLLA, where B is the middle block and is selected from one of the following polymer segments: poly(D,L-lactic acid) (PLA), polyethylene oxide (PEO), and polycaprolactone (PCL); b represents the block linkage symbol. B represents PLA and PEO, and the Flory-Huggins interaction parameter (χ²) between the middle block B and the chiral terminal block PLLA is... B / PLLA )χ<0.2 and the domain thickness of the B block is less than 10 nm; chiral triblock copolymers can form H* helical phases through self-assembly; B represents PCL, and the Flory-Huggins interaction parameter (χ²) between the middle block B and the chiral terminal block PLLA is... B / PLLA )χ<0.2 and the domain thickness of the B block is ≤7.2 nm.

[0011] The domain thickness of the B-block is L × N 2 / 3 , where L is the repeating unit length of the middle block B, in nm; N is the degree of polymerization of the middle block B.

[0012] The method for preparing the chiral triblock copolymer includes the following steps: The AB-type diblock copolymer precursor PS-bB-OH with a hydroxyl end was synthesized by atom transfer radical polymerization (ATRP) or reversible addition-fragmentation chain transfer (RAFT) polymerization. Using PS-bB-OH as a macromolecular initiator, the target product PS-bBb-PLLA was obtained through ring-opening polymerization (ROP) of L-lactide catalyzed by stannous octoate Sn(Oct)2.

[0013] The chiral triblock copolymer is used in transdomain chiral transfer.

[0014] A method for constructing a self-assembled material with a helical nanostructure using the chiral triblock copolymer includes the following steps: 1) Dissolve the chiral triblock copolymer in a volatile organic solvent (such as dichloromethane, chloroform, tetrahydrofuran, toluene, etc.) to prepare a solution with a concentration of 0.5-5 wt%; 2) The solvent is slowly evaporated at room temperature by solution casting to form a bulk self-assembled sample.

[0015] The resulting sample was dried under vacuum to completely remove residual solvent.

[0016] B represents PLA or PEO, and the χ of the chiral triblock copolymer... B / PLLA Nanostructured materials with H* helical phases can be obtained when the thickness of the mid-block is <0.2 and the domain thickness of the mid-block is <10 nm.

[0017] B represents PCL, and the χ of the chiral triblock copolymer... B / PLLA Nanostructured materials with H* helical phases can be obtained when the thickness of the intermediate block is less than 0.2 nm and the domain thickness of the intermediate block is less than 7.2 nm.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention provides six different medium-block ABC* type chiral triblock copolymers, establishing a complete material platform for studying transdomain chiral transfer.

[0019] (2) This invention is the first to clearly disclose the compatibility (χ) between intermediate blocks and chiral blocks. B / PLLA The ) is the "switch" that determines whether chiral transmission can occur, while the length of the middle segment is the "dimmer" that determines the transmission distance, proposing a clear control rule of "transmission if compatible and short, and interruption if incompatible or long".

[0020] (3) This invention regulates the final self-assembled structure by using the χ parameter and chain length, providing a reliable and quantifiable theoretical basis and design criteria for the directional design and preparation of polymer materials with specific nanostructures.

[0021] (4) This invention prepares materials with chiral helical nanostructures and non-chiral columnar phase structures by precise control, and can prepare advanced functional materials such as chiral photonic crystals, circularly polarized light-emitting materials, and chiral separation membranes as needed. Attached Figure Description

[0022] Figure 1 The diagram shows the chemical structures of the six triblock copolymers of the present invention and their corresponding χ-parameters and self-assembly behavior classification diagram. Figure 2 The NMR spectra of SA-LA and SA-OH prepared in Example 1; Figure 3 GPC diagrams of SA-LA and SA-OH prepared in Example 1; Figure 4 shows the NMR spectra of SE-LA and SE-OH prepared in Example 2; Figure 5GPC diagrams of SE-LA and SE-OH prepared in Example 2; Figure 6 The NMR spectra of SV-LA and SV-OH prepared in Example 3; Figure 7 GPC diagrams of SE-LA, SE-OH, and CTA-P4VP-OH prepared in Example 3; Figure 8 shows the NMR spectra of SC-OH and SC-LA prepared in Example 4; Figure 9 GPC diagrams of PS-OH, SC-OH, and SC-LA prepared in Example 4; Figure 10 The NMR spectra of SS-OH and SS-LA prepared in Example 5; Figure 11 GPC diagrams of CTA-P4CS-OH, SS-OH, and SS-LA prepared in Example 5; Figure 12 The NMR spectra of SM-OH and SM-LA prepared in Example 6; Figure 13 GPC diagrams of CTA-PMMA, SM-OH, and SM-LA prepared in Example 6; Figure 14 TEM images and SAXS spectra of the self-assembled products of SA-LA prepared in Example 1, SE-LA prepared in Example 2, and SC-LA prepared in Example 4; Figure 15 TEM images and SAXS spectra of the SV-LA prepared in Example 3, the SS-LA prepared in Example 5, and the SM-LA prepared in Example 6, which self-assembled to form achiral columnar phases; Figure 16 S prepared in Example 4 40 -C4-LA 19 TEM images and SAXS spectra; Figure 17 For (a) S prepared in Example 3 28 -V6-LA 19 (b) S prepared in Example 5 33 -S 17 -LA 26 and (c) S prepared in Example 6 35 -M5-LA 17 TEM image (RuO4 staining) of the self-assembled columnar phase and the corresponding SAXS spectrum (d). Figure 18 This is a schematic diagram of the self-assembled phase diagram of the present invention. Detailed Implementation

[0023] The present invention will be described in further detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0024] A method for regulating the chiral structure and chiral transfer of triblock copolymers via a mid-block copolymer includes the following steps: (1) Select a triblock copolymer. The general structural formula of the triblock copolymer is PS-bBb-PLLA, where B is the middle block and B is selected from one of the following polymer segments: poly(D,L-lactic acid) (PLA), polyethylene oxide (PEO), polycaprolactone (PCL), poly(4-vinylpyridine) (P4VP), poly(4-chlorostyrene) (P4CS), polymethyl methacrylate (PMMA); that is, triblock copolymers PS-PLA-PLLA (denoted as SA-LA), PS-PEO-PLLA (denoted as SE-LA), PS-PCL-PLLA (denoted as SC-LA), PS-P4VP-PLLA (denoted as SV-LA), PS-P4CS-PLLA (denoted as SS-LA), PS-PMMA-PLLA (denoted as SM-LA); (2) By regulating the self-assembly behavior of the triblock copolymer through the middle block B, the transdomain chiral transfer and the final nanostructure can be controlled. The regulation specifically involves: S1) determining the Flory-Huggins interaction parameter (χ²) between the mid-block B and the chiral terminal block PLLA. B / PLLA When χ < 0.2, there is a possibility of cross-domain chiral transmission, and B is PLA, PEO, or PCL; when χ > 0.2, cross-domain chiral transmission is suppressed, and self-assembly into chiral structures occurs, and B is P4VP, P4CS, or PMMA. When S2)B is PLA, PEO, or PCL, the chain length of the middle block B is further determined. B represents PLA or PEO. The domain thickness of segment B is calculated using the formula: L × N. 2 / 3 When the thickness (where L is the length of the repeating unit of the middle block B and N is the degree of polymerization of the middle block B) is less than 10 nm, it self-assembles to form a helical phase, i.e., a chiral structure; when the thickness exceeds 10 nm, chiral transfer is blocked, and it self-assembles to form a non-chiral columnar phase. B is a PCL segment. When the domain thickness of the B segment is ≤7.2 nm, it self-assembles to form a helical phase, i.e., a chiral structure. When the thickness is ≥7.6 nm, chiral transmission is blocked, and it self-assembles to form a non-chiral columnar phase.

[0025] The length L of the B-block repeating unit can be obtained theoretically from polymer handbooks (e.g., calculated from single bond lengths and bond angles), or estimated experimentally by determining its chain conformation and statistical segment lengths (e.g., Kuhn lengths) using methods such as wide-angle X-ray scattering (WAXS). The Flory-Huggins interaction parameter χ... B / PLLA Typical values ​​can be obtained by consulting polymer handbooks, or by analyzing the order-disorder transition temperature using experimental methods such as small-angle X-ray scattering (SAXS), calculating it using the thermodynamic properties of the melt or solution (such as the enthalpy of mixing), or determining it using techniques such as neutron scattering.

[0026] Schematic diagram of the chemical structure of the six triblock copolymers involved in this invention (a) and their corresponding χ. mid-block / PLLA Parameter diagram (b) as follows Figure 1 As shown.

[0027] χ B / PLLA :PLA / PLLA: 0.001, PEO / PLLA: 0.079, PCL / PLLA: 0.103, P4VP / PLLA: 0.316, P4CS / PLLA: 0.339, PMMA / PLLA: 0.413.

[0028] Example 1: Synthesis and self-assembly of PS-PLA-PLLA (SA-LA) Synthesis: PS-OH was synthesized via ATRP using the dual-headed initiator Br-OH. PS-PLA-OH (SA-OH) was then synthesized via ROP of D,L-lactide using PS-OH as a macromolecular initiator and Sn(Oct)2 as a catalyst. Finally, SA-LA was synthesized via ROP of L-lactide using SA-OH as a macromolecular initiator. 40 -A4-LA 20 S 40 -A 10 -LA 17、 S 40 -A 18 -LA 4、 S 40 -A4-OH,S 40 -A 10 -OH 、 S 40 -A 18 -OH 1 H NMR image as follows Figure 2 As shown, the GPC diagram is as follows Figure 3 As shown. S 40 -A4-LA 20 S 40 -A 10 -LA17、 S 40 -A 18 The characterization parameters of -LA4 are shown in Table 1. In this embodiment, the amount of each substance used in the preparation of each product was calculated based on the target molecular weight, expressed in S... 40 -A4-LA 20 For example: retrieve PS 40 -OH (Mn = 39.8 kg / mol, 1.0 equiv), D,L-lactide (for SA-OH) or L-lactide (for SA-LA) (monomer / initiator molar ratio calculated based on target molecular weight, e.g., for S...) 40 -A4-OH, D,L-lactide (approximately corresponding to Mn = 3.7 kg / mol), Sn(Oct)2 (catalyst, [M] / [Sn] molar ratio = 1000:1), reacted in toluene at 110 °C for 24 hours. Other samples achieved different chain lengths by adjusting the monomer / initiator ratio and reaction time.

[0029] Example 2: Synthesis and self-assembly of PS-PEO-PLLA (SE-LA) and critical chain length effect Synthesis: Commercially available dihydroxy PEO was brominated at one end to give Br-PEO-OH. PS-PEO-OH (SE-OH) was then synthesized via ATRP. Finally, PLLA was grafted onto PLLA via ROP to obtain SE-LA. 43 -E 0.4 -OH,S 53 -E1-OH, S 47 -E 10 -OH S 43 -E 0.4 -LA 28 S 53 -E1-LA 23 S 47 -E 10 -LA 11 During the preparation of each substance, the block length is controlled by changing the initial molecular weight of PEO and the amount of L-lactide added, based on the target molecular weight calculation.

[0030] With S 43 -E 0.4 -LA 28 For example: Take Br-PEO 0.4 -OH (Mn = 0.4 kg / mol, 1.0 equiv), styrene (target PS Mn = 43 kg / mol), CuBr / PMDETA catalytic system, ATRP in toluene at 90 °C. The resulting S 43 -E 0.4-OH groups reacted with L-lactide (target PLLA Mn = 28 kg / mol) in toluene at 110 °C under Sn(Oct)2 catalysis for ROP reaction. Other samples were prepared using similar methods.

[0031] S 43 -E 0.4 -LA 28 S 53 -E1-LA 23 S 47 -E 10 -LA 11 S 43 -E 0.4 -OH,S 53 -E1-OH, S 47 -E 10 -OH 1 H NMR image as follows Figure 4 As shown, the GPC diagram is as follows Figure 5 As shown. S 43 -E 0.4 -LA 28 S 53 -E1-LA 23 S 47 -E 10 -LA 11 The characterization parameters are shown in Table 1.

[0032] Example 3: Synthesis of PS-P4VP-PLLA (SV-LA) Synthesis: P4VP-OH homopolymer was synthesized via RAFT polymerization. PS-P4VP-OH (SV-OH) was then synthesized via RAFT. Finally, PLLA was grafted onto PLLA via ROP to obtain SV-LA. 31 -V1-OH, S 31 -V1-LA 19 S 28 -V6-OH、S 28 -V6-LA 19 Each preparation method is calculated based on the target molecular weight and achieved by varying the molecular weight of P4VP-OH and the amount of styrene added. (The last sentence appears to be incomplete and possibly refers to a different process.) 31 -V1-LA 19 For example: First, synthesize P4VP1-OH (Mn=1.2 kg / mol, CTA is DMP-OH, AIBN initiation, reaction in THF at 60℃). Use this as a macromolecular RAFT reagent, and RAFT polymerize it with styrene (target PS Mn=31 kg / mol) in THF at 60℃ under AIBN initiation to obtain S. 31-V1-OH. Then, it undergoes a ROP reaction with L-lactide (target PLLA Mn = 19 kg / mol) catalyzed by Sn(Oct)2. The preparation methods for other samples are similar.

[0033] S 31 -V1-LA 19 S 28 -V6-LA 19 S 31 -V1-OH, S 28 -V6-OH 1 H NMR image as follows Figure 6 As shown, the GPC diagram is as follows Figure 7 As shown. S 31 -V1-LA 19 S 28 -V6-LA 19 The characterization parameters are shown in Table 1.

[0034] Figure 6 and 7 CTA-P4VP-OH refers to a poly(4-vinylpyridine) with hydroxyl end capped by a chain transfer agent (CTA). It can be prepared by RAFT polymerization using a hydroxyl-containing chain transfer agent (such as DMP-OH) and 4-vinylpyridine monomer.

[0035] Example 4: Synthesis of PS-polycaprolactone-PLLA (SC-LA) Synthesis: Polystyrene (PS-OH) was synthesized via ATRP using the bis-headed initiator 3-hydroxy-2,2-dimethylpropyl-2-bromo-2-methylpropionate (Br-OH). PS-polycaprolactone (PS-PCL-OH, denoted as SC-OH) was then synthesized via ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) using PS-OH as a macromolecular initiator and stannous octoate (Sn(Oct)2) as a catalyst. Finally, the target product PS-PCL-PLLA (SC-LA) was synthesized via ROP of L-lactide using SC-OH as a macromolecular initiator. 40 -C2-OH, S 40 -C4-OH, S 40 -C 10 -OH,S 40 -C2-LA 20 S 40 -C4-LA 19 S 40 -C 10 -LA 12Each was prepared by adjusting the amounts of ε-CL and L-lactide based on the target molecular weight. 40 -C2-LA 20 For example: retrieve PS 40 -OH (Mn = 39.8 kg / mol, 1.0 equiv), ε-CL (target PCL Mn = 2.3 kg / mol), Sn(Oct)₂ catalysis, ROP in toluene at 110 °C yields S 40 -C2-OH. Then, under the same conditions, ROP is performed with L-lactide (target PLLA Mn = 20 kg / mol) to obtain S. 40 -C2-LA 20 .

[0036] S 40 -C2-LA 20 S 40 -C4-LA 19 S 40 -C 10 -LA 12 S 40 -C2-OH, S 40 -C4-OH, S 40 -C 10 -OH 1 H NMR image as follows Figure 8 As shown, the GPC diagram is as follows Figure 9 As shown. S 40 -C2-LA 20 S 40 -C4-LA 19 S 40 -C 10 -LA 12 The characterization parameters are shown in Table 1.

[0037] Figure 8 and 9 PS-OH refers to polystyrene with hydroxyl groups at the end, which can be prepared by polymerization of styrene monomers with a bi-headed initiator Br-OH (such as 3-hydroxy-2,2-dimethylpropyl-2-bromo-2-methylpropionate) using the ATRP method.

[0038] Example 5: Synthesis of PS-poly(4-chlorostyrene)-PLLA (SS-LA) Synthesis: Hydroxylated RAFT chain transfer agent DMP-OH was synthesized. Using AIBN as an initiator and DMP as a chain transfer agent, hydroxyl-terminated poly(4-chlorostyrene) homopolymer (P4CS-OH) was synthesized via RAFT polymerization. Using P4CS-OH as a macromolecular RAFT agent, PS-P4CS-OH (denoted as SS-OH) was synthesized via RAFT polymerization. Finally, using SS-OH as a macromolecular initiator, the target product PS-P4CS-PLLA (SS-LA) was synthesized via ROP of L-lactide. 42 -S2-LA 21 S 33 -S 17 -LA 26、 S 42 -S2-OH, S 33 -S 17 The -OH groups are prepared by varying the molecular weight of P4CS-OH and the amount of styrene added. 42 -S2-LA 21 For example: First, synthesize P4CS2-OH (Mn=2.1 kg / mol, CTA is DMP-OH, AIBN initiator, reaction in toluene at 70℃). Use this as a macromolecular RAFT reagent, and RAFT polymerize it with styrene (target PS Mn=42 kg / mol) in toluene at 70℃ under AIBN initiation to obtain S. 42 -S2-OH. Then, it undergoes a ROP reaction with L-lactide (target PLLA Mn=21 kg / mol) under Sn(Oct)2 catalysis.

[0039] S 42 -S2-LA 21 S 33 -S 17 -LA 26、 S 42 -S2-OH, S 33 -S 17 -OH 1 H NMR image as follows Figure 10 As shown, the GPC diagram is as follows Figure 11 As shown. S 42 -S2-LA 21 S 33 -S 17 -LA 26 The characterization parameters are shown in Table 1.

[0040] Figure 10 and 11CTA-P4CS-OH refers to poly(4-chlorostyrene) with hydroxyl end capped by a chain transfer agent (CTA). It can be prepared by RAFT polymerization using a hydroxyl-containing chain transfer agent (such as DMP-OH) and 4-chlorostyrene monomer.

[0041] Example 6: Synthesis and self-assembly of PS-poly(methyl methacrylate)-PLLA (SM-LA) Synthesis: Ahydroxyl-terminated polymethyl methacrylate homopolymer (PMMA-OH) was synthesized via RAFT polymerization using AIBN as the initiator and DMP as the chain transfer agent. PS-PMMA-OH (denoted as SM-OH) was then synthesized via RAFT polymerization using PMMA-OH as a macromolecular RAFT agent. Finally, the target product PS-PMMA-PLLA (SM-LA) was synthesized via ROP of L-lactide using SM-OH as a macromolecular initiator. 37 -M3-LA 14 S 35 -M5-LA 17 S 37 -M3-OH, S 35 The preparation of -M5-OH is achieved by changing the molecular weight of PMMA-OH and the amount of styrene added. (The last part, "S," appears to be a typo and can be left as is.) 37 -M3-LA 14 For example: First, synthesize PMMA3-OH (Mn=3.0 kg / mol, CTA is DMP-OH, AIBN initiator, reaction in toluene at 70℃). Use this as a macromolecular RAFT reagent, and RAFT polymerize it with styrene (target PS Mn=37 kg / mol) in toluene at 70℃ under AIBN initiation to obtain S. 37 -M3-OH. Then, it undergoes a ROP reaction with L-lactide (target PLLA Mn = 14 kg / mol) under Sn(Oct)2 catalysis.

[0042] S 37 -M3-LA 14 S 35 -M5-LA 17 S 37 -M3-OH, S 35 -M5-OH 1 H NMR image as follows Figure 12 As shown, the GPC diagram is as follows Figure 13 As shown. S 37 -M3-LA 14 S 35 -M5-LA 17 The characterization parameters are shown in Table 1.

[0043] Figure 12 and 13 CTA-PMMA refers to polymethyl methacrylate (PMMA) capped with a chain transfer agent (CTA). It can be prepared by RAFT polymerization using a chain transfer agent (such as DMP, which does not contain hydroxyl groups) and methyl methacrylate monomers. If a hydroxyl group (PMMA-OH) is required at the end, a chain transfer agent containing hydroxyl groups (such as DMP-OH) must be used.

[0044] Self-assembly and chiral transfer (1) The S prepared in Example 1 40 -A4-LA 20 (Subscripts indicate the nominal molecular weight of each block, in kg / mol) Prepare a 1 wt% dichloromethane solution, and allow it to slowly evaporate at room temperature to form a film, completing the S... 40 -A4-LA 20 Self-assembly. TEM test results are as follows: Figure 14 (a), SAXS diagram as shown Figure 14 (e). The results show that it formed a clear H* helical phase.

[0045] (2) The S prepared in Example 2 43 -E 0.4 -LA 28 (Short mid-segment) undergoes self-assembly, TEM image as follows Figure 14 (b), SAXS diagram as follows Figure 14 (e). Formation of the H* phase.

[0046] (3) S prepared in Example 3 31 -V1-LA 19 (Even if the mesoblock is very short) self-assembly is performed, TEM image as follows Figure 15 (a), SAXS diagram as shown Figure 15 (d). The results clearly show that it forms a non-chiral columnar phase. This proves that when χ B / PLLA When the value is too high (0.316>0.2), chiral transmission is completely suppressed.

[0047] S prepared in Example 3 28 -V6-LA 19 (Even if the mesoblock is very short) self-assembly is performed, TEM image as follows Figure 17 (a), SAXS diagram as shown Figure 17 (d).

[0048] (4) The S prepared in Example 4 40 -C2-LA 20 A 2 wt% dichloromethane solution was prepared using a medium-block PCL (molecular weight 2,300 g / mol), and the film was formed by slow evaporation at room temperature via solution casting, completing the S... 40-C2-LA 20 Self-assembly. TEM image as follows. Figure 14 (c), SAXS as Figure 14 (e). The results show that a clear H* helical phase was formed, indicating that chirality was successfully transferred across the blocks in the PCL at this length.

[0049] The S prepared in Example 4 40 -C4-LA 19 (Medium-block PCL, molecular weight 3,900 g / mol) self-assembled under the same conditions, TEM image as follows. Figure 16 (a), SAXS as Figure 16 As shown in (b), it is confirmed that it can still form an H* helical phase.

[0050] The S prepared in Example 4 40 -C 10 -LA 12 (Medium-block PCL, molecular weight 9,500 g / mol) self-assembled under the same conditions, TEM image as follows. Figure 14 (d), SAXS diagram as follows Figure 14 (e) The results showed that it formed a non-chiral columnar phase (C phase).

[0051] Effect Comparison: This series of copolymers has similar χ² values. PCL / PLLA The value (0.103) differs, but the mesoblock length varies. Experimental results demonstrate that for the SC-LA system, there exists a critical PCL chain length; below this critical value, chiral transfer occurs, forming the H* phase; above this value, chiral transfer is suppressed, forming the C phase. This clearly demonstrates the regulatory role of mesoblock length on transdomain chiral transfer. 40 -C 10 -LA 12 The calculated thickness of the block domain in PCL is approximately 7.6 nm, forming the C phase; for the block system in PCL, its critical domain thickness may be around 7.2 nm (S 40 -C4-LA 19 H* phase) to 7.6nm (S 40 -C 10 -LA 12 Between (C phase). Figure 14 In the e-figure, √3, √7, etc., are the ratios of the positions of the SAXS diffraction peaks used to identify the phase structure.

[0052] (5) The S prepared in Example 5 42 -S2-LA 21 A 2 wt% dichloromethane solution was prepared using a medium-block P4CS molecular weight of 2,100 g / mol, and then slowly evaporated to form a film at room temperature via solution casting. TEM ( Figure 15(b) and SAXS ( Figure 15 (d) The results showed that it formed a non-chiral columnar phase.

[0053] The S prepared in Example 5 33 -S 17 -LA 26 (Medium-block P4CS, molecular weight 17,000 g / mol) self-assembles under the same conditions, TEM results are as follows. Figure 17 (b) SAXS diagram as shown Figure 17 (d). The results also show a columnar phase.

[0054] Effect description: Although S 42 -S2-LA 21 The middle segment is very short, but due to its χ P4CS / PLLA The value is very high (0.339 > 0.2), and chiral transmission is completely suppressed. Even with further increases in the interblock length (S... 33 -S 17 -LA 26 Even with this, the H* phase still cannot be formed. This proves that when χ... mid-block / PLLA Once the critical value is exceeded, the length of the inter-block is no longer the determining factor, and chiral transmission is essentially blocked.

[0055] (6) The S prepared in Example 6 37 -M3-LA 14 A 2 wt% dichloromethane solution was prepared using a medium-block PMMA (molecular weight 3,000 g / mol) and slowly evaporated to form a film at room temperature via solution casting. TEM image shown. Figure 15 (c) and SAXS diagram as shown Figure 15 (d). The results showed that it formed a non-chiral columnar phase.

[0056] The S prepared in Example 6 35 -M5-LA 17 (Medium-block PMMA, molecular weight 5,000 g / mol) self-assembled under the same conditions, TEM image as follows. Figure 17 (c), SAXS diagram as follows Figure 17 (d). The results also show a columnar phase.

[0057] Performance Description: Similar to SS-LA and SV-LA, this system exhibits a high χ² value. PMMA / PLLA The value (0.413>0.2) indicates that, regardless of the length of the mesoblock PMMA (from 3,000 g / mol to 5,000 g / mol), its self-assembly was suppressed to form an achiral columnar phase, further verifying the blocking effect of highly incompatible mesoblocks on transdomain chiral transfer.

[0058] Table 1. Information on the synthesized triblock copolymers involved in this invention.

[0059] This invention modulates the compatibility (χ²) of medium blocks (B) with chiral blocks (PLLA) by selecting medium blocks (B) with different chemical structures. B / PLLA By combining this with the design of the mid-block length, precise control of the "cross-domain chirality transfer" process can be achieved, thereby enabling the controlled preparation of chiral helical (H*) or achiral columnar (C) nanostructures.

Claims

1. A method for controlling the chiral structure and chiral transmission of a mid-blocked triblock copolymer, characterized by: Comprising the following steps: Firstly, a triblock copolymer is provided, the general structure of the triblock copolymer is PS-b-B-b-PLLA, B is a middle block, B is selected from one of the following polymer segments: poly(D,L-lactic acid) PLA, polyethylene oxide PEO, polycaprolactone PCL, poly(4-vinylpyridine) P4VP, poly(4-chlorostyrene) P4CS, polymethyl methacrylate PMMA; b represents a block connector; PLLA is a chiral poly-L-lactic acid segment; PS is a polystyrene segment; Then the self-assembly behavior of the triblock copolymer is regulated by the middle block B; The regulation is specific: 1) determine the Flory-Huggins interaction parameter χ between midblock B and chiral endblock PLLA B / PLLA ​ When χ < 0.2, there is a possibility of cross-domain chiral transfer; at this time, B is PLA, PEO, PCL; When χ > 0.2, cross-domain chiral transfer is inhibited, and self-assembly forms achiral structure; at this time, B is P4VP, P4CS, PMMA; 2) When B is a PLA, PEO, PCL segment, the chain length of the middle block B is determined; When B is a PLA, PEO segment, when the domain thickness of the B block is less than 10 nm, self-assembly forms a helical phase, i.e. a chiral structure; when the thickness exceeds 10 nm, chiral transfer is blocked, and self-assembly forms an achiral columnar phase; When B is a PCL segment, when the domain thickness of the B block is ≤7.2 nm, self-assembly forms a helical phase, i.e. a chiral structure; when the thickness is ≥7.6 nm, chiral transfer is blocked, and self-assembly forms an achiral columnar phase.

2. The method of claim 1, wherein the chiral structure of the midblock-regulated triblock copolymer and the chirality transfer are characterized by: The domain thickness of the midblock B = L x N 2 / 3 wherein L is the length of the repeating unit of the midblock B in nm; and N is the degree of polymerization of the midblock B.

3. A chiral tri-block copolymer characterized by: The general structure is PS-b-B-b-PLLA, B is a middle block, B is selected from one of the following polymer segments: poly(D,L-lactic acid) PLA, polyethylene oxide PEO, polycaprolactone PCL; b represents a block connector; PLLA is a chiral poly-L-lactic acid segment; PS is a polystyrene segment; the Flory-Huggins interaction parameter χ between the middle block B and the chiral end block PLLA is < 0.2; When B is a PLA, PEO, when the domain thickness of the middle block B is less than 10 nm, the chiral triblock copolymer can self-assemble to form a H* helical phase; When B is a PCL segment, when the domain thickness of the middle block B is ≤7.2 nm, the chiral triblock copolymer can self-assemble to form a H* helical phase.

4. The chiral tri-block copolymer based on mid-block regulation according to claim 3, wherein: Domain thickness of the B block = L x N 2 / 3 where L is the length of the repeating unit of the mid-block B in nm, and N is the degree of polymerization of the mid-block B.

5. Process for the preparation of a chiral tri-block copolymer according to any one of claims 3 to 4, characterized in that: Comprising the following steps: An AB type diblock copolymer precursor PS-b-B-OH with a hydroxyl group at one end is synthesized by atom transfer radical polymerization or reversible addition-fragmentation chain transfer polymerization; The target product PS-b-B-b-PLLA is obtained by ring-opening polymerization of L-lactide under the catalysis of stannous octoate Sn(Oct)2, taking PS-b-B-OH as a macromolecular initiator.

6. The chiral triblock copolymer according to any one of claims 3-4 for use in cross-domain chiral transfer.

7. Use of a chiral tri-block copolymer according to any one of claims 3 to 4, characterized in that: The chiral triblock copolymer is used for preparing self-assembled materials with helical nanostructures.

8. A method for constructing a self-assembled material having a helical nanostructure using the chiral tri-block copolymer according to any one of claims 3 to 4, characterized by: Comprising the following steps: 1) Dissolve the chiral triblock copolymer in a volatile organic solvent to prepare a solution with a concentration of 0.5-5 wt%; the chiral triblock copolymer is as defined in any one of claims 3-4; 2) by solution casting method, slowly evaporate the solvent at room temperature, form bulk self-assembly sample; the self-assembly material has the nanostructure self-assembly material of helical phase.

9. The method of claim 7, wherein: The volatile organic solvent is one or more of dichloromethane, chloroform, tetrahydrofuran and toluene.

10. Use of the chiral tri-block copolymer according to any one of claims 3-4 for the preparation of a circularly polarized luminescent material, a chiral sensor, a chiral separation membrane or a drug controlled release carrier.

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