Free radical-polymerizable compounds, polymerizable compositions, and polymerizates and optical articles formed therefrom

Abstract

The present disclosure is directed to free radical-polymerizable compounds, polymerizable compositions, and polymerizates and optical articles prepared therefrom. The free radical-polymerizable compound comprises: (a) a thio(meth)acrylate functional group; (b) an aromatic group.; (c) a thioketal and / or thioacetal group directly bonded to the aromatic group (b); and (d) a thioether functional linking group directly bonded to the thio(meth)acrylate functional group and the thioketal and / or thioacetal group. A particular example of a free radical-polymerizable compound has the structure: wherein X comprises H, an alkyl group or an aryl group, Ar comprises an aromatic group, or X and Ar together form a fused ring structure.

Description

FREE RADICAL-POLYMERIZABLE COMPOUNDS, POLYMERIZABLE COMPOSITIONS, AND POLYMERIZATES AND OPTICAL ARTICLES FORMEDTHEREFROM FIELD OF THE DISCLOSURE

[0001] The present disclosure provides free radical-polymerizable compounds,polymerizable compositions, polymerizates formed from the polymerizable compositions, and optical articles formed from the polymerizates. BACKGROUND

[0002] Polymeric materials such as plastics have been developed asalternatives and replacements for silica-based inorganic glass in various optical applications such as lenses, fiber optics, display screens, windows and automotive, nautical and aviation transparencies. These polymeric materials can provide advantages relative to glass, including but not limited to shatter resistance, lighter weight, ease of molding and ease of dyeing. Representative examples of suchpolymeric materials known in the art include poly(methyl methacrylate), polycarbonateand poly(diethylene glycol bis(allylcarbonate)).

[0003] In general, the refractive index (RI) of a polymeric material is lower thanthat of high index glass. For example, the refractive index of poly(diethylene glycolbis(allylcarbonate)) is about 1.50, compared to that of high index glass, which canrange from about 1.60 to 1.80.

[0004] The preparation of a polymeric material having a refractive index greaterthan 1.50 is known in the art. The materials from which lenses, and in particular opticallenses, are fabricated can be categorized by refractive index. In general, “low refractive index” can include indices of refraction of from less than 1.50 through 1.53; “middle refractive index” can include indices of refraction of from 1.54 through 1.57; “high refractive index” can include indices of refraction of from 1.58 through 1.66; and “ultra-high refractive index” can include indices of refraction of 1.67 and greater.

[0005] Ultra-high RI polymers are typically thermally cured, polythiourethanepolymers prepared from thiols and aromatic isocyanates. However, isocyanates havedrawbacks. Health effects associated with isocyanate exposure can include skin irritation, eye irritation, chest tightness and difficulty breathing.

[0006] It is desirable to identify new polymerizable organic compounds, whichcan be used to prepare transparent polymerizates that possess high and ultra-highrefractive indices without the need for isocyanates.SUMMARY OF THE DISCLOSURE

[0007] The present disclosure is directed to free radical-polymerizablecompounds, polymerizable compositions, and polymerizates and articles; in particular,optical articles, prepared therefrom. The free radical-polymerizable compoundcomprises: (a) a thio(meth)acrylate functional group; (b) an aromatic group.; (c) athioketal and / or thioacetal group directly bonded to the aromatic group (b); and (d) a thioether functional linking group directly bonded to the thio(meth)acrylate functional group and the thioketal and / or thioacetal group.

[0008] The present disclosure accordingly also provides a polymerizablecomposition comprising such free radical-polymerizable compounds as describedabove and in further detail below, as well as a polymerizate formed from suchcomposition and articles, in particular optical articles, made therefrom. Suchpolymerizates and articles demonstrate high and ultra-high refractive indices,prepared without the need for isocyanates. DETAILED DESCRIPTION

[0009] It is noted that, as used in this specification and the appended claims,the singular forms “a”, “an”, and “the” include plural referents, unless expressly andunequivocally limited to one referent.

[0010] For the purposes of this specification, unless otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions, and other parameters used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the disclosed composition. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0011] All numerical ranges herein include all numerical values and ranges ofall numerical values within the recited numerical ranges. Notwithstanding that thenumerical ranges and parameters setting forth the broad scope of the disclosure areapproximations, the numerical values set forth in the specific examples are reportedas precisely as possible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in their respective testing measurements.

[0012] The various examples presented herein are each understood to be non-limiting with respect to the scope of the disclosure.

[0013] As previously mentioned, the present disclosure is directed to an organicpolymerizable composition, and polymerizates and optical articles prepared therefrom. The term "optical quality", as used for example in connection with polymeric materials, e.g., a "resin of optical quality" or "organic polymeric material of optical quality" means that the indicated material, e.g., a polymeric material, resin, or resin composition, is or forms a substrate, layer, film or coating that can be used as an optical article, such asa lens, or in combination with an optical article.

[0014] The term "optical article" means that the specified article, at a thicknessof 3.5 mm, exhibits a light transmittance value (transmits incident light) of at least 4percent, such as at least 50 percent, or at least 70 percent, or at least 85 percent. As used herein, optical articles may demonstrate a light transmittance (% Transmittance,as defined by Equation 1 below , where I is the light transmitted through the article andIo is the incident light) of at least 70% when measured at 550 nanometers by, forexample, a Hunter UltraScan PRO (Hunter Associates Laboratory, Inc.) using D65 illuminant. Equation 1. % = 100 /

[0015] The term "optical article " further means that the specified article exhibitsa haze value of less than 5 percent, e.g., less than 1 percent or less than 0.5 percent, when the haze value is measured at 550 nanometers by, for example, a Haze Gard Plus Instrument, available from BYK-Gardner. Optical articles include, but are not limited to, lenses, optical layers, e.g., optical resin layers, optical films and optical coatings, and optical substrates having a light influencing property. As noted above,non-homogeneity due to incompatibility of components may manifest itself in the formof a milky appearance (“opacity”), especially in tinted or darkened articles (ex. sunlenses, polarized lenses, etc.) and becomes more apparent as the thickness of thearticle increases. In such cases, measurement of opacity at a constant thickness using an opacimeter or spectrophotometer can serve as a means of quantifying the phenomenon. Opacity is usually determined by one or more measurements ofreflectance of visible light through an article. For example, opacity may be calculatedfrom a ratio of diffuse reflectance measurements of the article with a black backingand the article with a white backing. The optical articles of this disclosure typicallyexhibit an opacity value of less than 28 percent, e.g., less than 27 percent, when the opacity value is measured, for example, using an EEL 12M Opacimeter, available fromSmithers, or an Ultra Scan PRO spectrophotometer, available from HunterLab, at anarticle thickness of 8 mm.

[0016] The free radical-polymerizable compound as disclosed herein comprises(a) a thio(meth)acrylate functional group. As used herein, the terms “(meth)acrylate”,“(meth)acrylic”, and the like encompass both acrylic and methacrylic examples of a given compound or functional group. By “thio(meth)acrylate” is meant a(meth)acryloylthio group. The free radical-polymerizable compound typicallycomprises at least 1, or at least 2, thio(meth)acrylate functional groups (a). The freeradical-polymerizable compound typically comprises at most 6, or at most 4,thio(meth)acrylate functional groups (a). For example, the free radical-polymerizablecompound may comprise 1 to 6, or 1 to 4, or 2 to 6, or 2 to 4 thio(meth)acrylatefunctional groups (a).

[0017] Thio(meth)acrylate functional groups (a) may be derived from(meth)acrylic acid or anhydrides thereof, and / or (meth)acryloyl chloride, reacted witha thiol such as a polythiol, as described below.

[0018] The free radical-polymerizable compound as disclosed herein furthercomprises (b) an aromatic group and (c) a thioketal and / or thioacetal group directly bonded to the aromatic group (b). Note that the phrase “and / or” when used in a list is meant to encompass alternative embodiments including each individual component in the list as well as any combination of components. For example, the list “A, B, and / or C” is meant to encompass seven separate embodiments that include A, or B, or C, or A + B, or A + C, or B + C, or A + B + C.

[0019] In certain examples, the free radical-polymerizable compound maycomprise at least 1 thioketal functional groups (c). The free radical-polymerizablecompound may comprise at most 4, or at most 3, or at most 2, thioketal groups (c).For example, the free radical-polymerizable compound may comprise 1 to 4, or 1 to 3,or 1 to 2 thioketal groups (c), such as a single thioketal group (c). Likewise, in certainexamples, the free radical-polymerizable compound may comprise at least 1 thioacetalfunctional groups (c). The free radical-polymerizable compound may comprise at most4, or at most 3, or at most 2, thioacetal groups (c). For example, the free radical-polymerizable compound may comprise 1 to 4, or 1 to 3, or 1 to 2 thioacetal groups(c), such as a single thioacetal group (c).

[0020] The aromatic functional group (b) and thioketal functional group (c) maybe derived from an aromatic ketone. Exemplary aromatic ketones comprise for instance 2-fluorenone, 9-fluorenone, 2-halo-9-fluorenone, 4-halo-9-fluorenone, 1,4- dihalo-9-fluorenone, 2,7-dihalo-9-fluorenone, 9-fluorenone-2-aldehyde, 9-fluorenone- 4-aldehyde, 9-fluorenone-2,7-dialdehyde, benzophenone, 4,4’dihalobenzophenone, and / or anthraquinone. The aromatic functional group (b) and thioacetal functionalgroup (c) may be derived from an aromatic aldehyde. Exemplary aromatic aldehydescomprise for instance benzene-1,2-dicarbaldehyde, benzene-1,3-dicarbaldehyde,benzene-1,4-dicarbaldehyde, 9-fluorenone-2-aldehyde, 9-fluorenone-4-aldehyde, and / or 9-fluorenone-2,7-dialdehyde. The use of aromatic compounds comprising both keto and aldehyde functionality, such as 9-fluorenone-4-aldehyde or 9-fluorenone-2,7- dialdehyde, would yield both thioketal and thioacetal functional groups.

[0021] The free radical-polymerizable compound as disclosed herein furthercomprises (d) a thioether functional linking group; i. e., a thioether functional groupthat is directly bonded to the thio(meth)acrylate functional group and the thioketal and / or thioacetal group (thus serving as a “linking group”), which may be derived from a thioether functional polythiol.

[0022] Suitable thioether functional polythiols that form the thioether functionallinking group can include, for example, bis-(2-mercaptoethyl) sulfide (DMDS), 1,4-Dithiane-2,5-dimethanethiol, 2,5-dimercaptomethyl-1,4-dithiane (Formula (Ia) below),4-mercaptomethyl-3,6-dithia-1,8-octanedithiol (Ib), 7-hydroxymethyl-1,14-dimercapto- 3,6,9,12-tetrathiatetradecane (Ic), 7-[2-(hydroxyethyl)]-1,13-dimercapto-3,6,8,11- tetrathiatridecane, 4,8-bis(mercaptomethyl)-1,11-dimercapto-3,6,9-trithiaundecane(Id) or regioisomers of (Id) such as the 4,7- or 5,7-regioisomers, or combinations ofany of the foregoing. The compounds (Ia)-(Id) have the structures of Formula (Ia)-(Id)below:

[0023] In certain examples, the thioether functional polythiol may further oralternatively comprise:(i) a polythiol according to Formula (II):H S n S S S H wherein each n is (ii) a polythiolH S n S H S S n wherein each n is(iii) a :R R'wherein RC1 – C3 alkylgroup, The polythiols of Formulae (II) and (III), when used, are present in amounts lowenough to prevent the formation of a gel.

[0024] In an example of the present disclosure, a free radical-polymerizablecompound is provided, comprising: (a) a thio(meth)acrylate functional group;(b) an aromatic group;(c) a thioketal and / or thioacetal group directly bonded to the aromaticgroup (b); and (d) a thioether functional linking group between thethio(meth)acrylate functional group and the thioketal and / or thioacetal group, wherein the free radical-polymerizable compound has a structure according to Formula (V): OX Ar Owherein X comprises H, an alkyl group or an aryl group, and Ar comprises an aromaticgroup. X and Ar may together form a fused ring structure.

[0025] In a particular example of the present disclosure, the free radical-polymerizable compound has the structure (Va) below: S S S xS S Swherein x and y are

[0026] The free radical-polymerizable compounds described above may beprepared, for example, by reacting an aromatic ketone / aldehyde with a thioetherfunctional polythiol (as described above), and further reacting the obtained reactionproduct with a (meth)acrylating agent such as (meth)acrylic anhydride or(meth)acryloylchloride.

[0027] The present disclosure is further directed to polymerizable compositionscomprising one or more of the free radical-polymerizable compounds describedabove. The free radical-polymerizable compound may be present in the compositionin an amount of at least 5 percent by weight, or at least 10 percent by weight, or at least 25 percent by weight, or at least 35 percent by weight, or at least 50 percent byweight, based on the total weight of polymerizable components on the polymerizablecomposition. The free radical-polymerizable compound may be present in thecomposition in an amount of up to 100 percent by weight, or at most 99 percent byweight, or at most 95 percent by weight, or at most 80 percent by weight, or at most 70 percent by weight, or at most 60 percent by weight, based on the total weight of polymerizable components on the polymerizable composition. For example, the free radical-polymerizable compound may be present in the composition in an amount of 5 to 100 percent by weight, or 5 to 99 percent by weight, or 5 to 95 percent by weight, or 5 to 80 percent by weight, or 5 to 70 percent by weight, or 5 to 60 percent by weight, or 10 to 100 percent by weight, or 10 to 99 percent by weight, or 10 to 95 percent by weight, or 10 to 80 percent by weight, or 10 to 70 percent by weight, or 10 to 60 percentby weight, or 25 to 100 percent by weight, or 25 to 99 percent by weight, or 25 to 95percent by weight, or 25 to 80 percent by weight, or 25 to 70 percent by weight, or 25to 60 percent by weight, or 35 to 100 percent by weight, or 35 to 99 percent by weight, or 35 to 95 percent by weight, or 35 to 80 percent by weight, or 35 to 70 percent by weight, or 35 to 60 percent by weight, or 50 to 100 percent by weight, or 50 to 99 percent by weight, or 50 to 95 percent by weight, or 50 to 80 percent by weight, or 50 to 70 percent by weight, or 50 to 60 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.

[0028] The polymerizable composition may further comprise one or more otherpolymerizable monomers, such as a thio(meth)acrylate monomer. Examples include 2,5-bis(methacryloylthiomethyl)1,4-dithiane, 2-ethyl-2-((meth)acryloylthiomethyl)-1,3- bis[(meth)acryloylthio]propane, 1,2,3-tris[(meth)acryloylthio]propane, 2,2- bis[(meth)acryloylthiomethyl]-1,3-bis[(meth)acryloylthio]propane, 4- (meth)acryloylthiomethyl-3,6-dithia-1,8-bis[(meth)acryloylthio]octane, 1,3- bis[(meth)acryloylthio]-2-(meth)acryloyloxypropane, 1-(meth)acryloylthio-2,3- bis[(meth)acryloyloxy]propane, 1,2-bis[(meth)acryloylthio]-3- (meth)acryloyloxypropane, 7-(meth)acryloyloxymethyl-3,6,9,12-tetrathia-1,14- bis[(meth)acryloylthio]tetradecane, 7-[2-(meth)acryloyloxyethyl]-3,6,8,11-tetrathia- 1,13-bis[(meth)acryloylthio]tridecane, 4,8-bis[(meth)acryloylthiomethyl]-3,6,9-trithia-1,11-bis[(meth)acryloylthio]undecane, and / or regioisomers of 4,8-bis[(meth)acryloylthiomethyl]-3,6,9-trithia-1,11-bis[(meth)acryloylthio]undecane.

[0029] Additional suitable polymerizable monomers include monomers havinga single ethylenically unsaturated radically polymerizable group include mono(meth)acrylates such as cyclohexyl (meth)acrylate, butyl (meth)acrylate, methyl (meth)acrylate, isobornyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, ethyl (meth)acrylate; vinyl ethers, styrene, or combinations of any of the foregoing.

[0030] Examples of suitable monomers having more than one ethylenicallyunsaturated radically polymerizable group include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylate, trimethylolpropane poly(meth)acrylates, pentaerythritol poly(meth)acrylates, ditrimethylolpropane poly(meth)acrylates, dipentaerythritol poly(meth)acrylates, glycerol poly(meth)acrylates, bisphenol A di(meth)acrylate, ethoxylated bis-phenol A di(meth)acrylate, propoxylated bis-phenol A di(meth)acrylate, cyclohexane diol di(meth)acrylates, tris(2-hydroxyethyl)isocyanurate poly(meth)acrylates, divinyl benzene, or combinations of any of the foregoing.

[0031] The additional polymerizable monomers, when used, may be present inthe composition in an amount of at least 1 percent by weight, or 5 percent by weight, or at least 20 percent by weight, or at least 30 percent by weight, or at least 40 percent by weight, based on the total weight of polymerizable components on the polymerizable composition. The additional polymerizable monomers may be present in the composition in an amount of at most 95 percent by weight, or at most 90 percent by weight, or at most 75 percent by weight, or at most 65 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.

[0032] Polymerizable compositions provided by the present disclosure cancomprise a cure initiator such as a free radical initiator. Polymerizable compositions can comprise one or more free radial initiators such as thermally-activated free radical initiators or free radical initiators activated by actinic radiation. A thermally activated free radical initiator can become active at elevated temperature, such as at a temperature greater than 25°C.

[0033] Examples of suitable thermally activated free radical initiators includeorganic peroxy compounds, azobis(organonitrile) compounds, N-acyloxyamine compounds, O-imino-isourea compounds, or combinations of any of the foregoing. Examples of suitable organic peroxy compounds, that may be used as thermal polymerization initiators include peroxymonocarbonate esters, such as tertiary- butylperoxy 2-ethylhexyl carbonate and tertiary-butylperoxy isopropyl carbonate; peroxyketals, such as 1,1-di-(tert-butyl peroxy)-3,3,5-trimethylcyclohexane; peroxydicarbonate esters, such as di(2-ethylhexyl)peroxydicarbonate, di(secondary butyl)peroxydicarbonate and diisopropylperoxydicarbonate; diacylperoxides such as 2,4-dichlorobenzoyl peroxide, isobutyryl peroxide, decanoyl peroxide, lauryl peroxide, propionyl peroxide, acetyl peroxide, benzoyl peroxide, and p-chlorobenzoyl peroxide; peroxyesters such as tert-butylperoxy pivalate, tert-butylperoxy octylate, and tert- butylperoxyisobutyrate; methylethylketone peroxide, acetylcyclohexane sulfonyl peroxide, or combinations of any of the foregoing. Other examples of suitable peroxy compounds include 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, and / or 1,1- bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane. Examples of suitable azobis(organonitrile) compounds that may be used as thermal polymerization initiators-azobis(2-methyl-butanenitrile), and / or azobis(2 / 1- dimethylvaleronitrile). A thermally activated free radical initiator can comprise 1- acetoxy-2,2,6,6-tetramethylpiperidine and / or 1,3-dicyclohexyl-O—(N- cyclohexylideneamino)-isourea.

[0034] A free radical initiator can comprise a photoinitiator. Polymerizablecompositions provided by the present disclosure can include a photoinitiator or combination of photoinitiators. The radiation can be actinic radiation that can apply energy that can generate an initiating species from a photopolymerization initiator --rays, X-rays, ultraviolet (UV)light (including UVA, UVA, and UVC spectra), visible light, blue light, infrared, near-infrared, or an electron beam. For example, the photoinitiator can be a UVphotoinitiator.

[0035] -hydroxyketones,-diethoxyacetophenone, 4,4-diethylaminobenzophenone, 2,2- dimethoxy-2-phenylacetophenone, 4-isopropylphenyl 2-hydroxy-2-propyl ketone, 1- hydroxycyclohexyl phenyl ketone, isoamyl p-dimethylaminobenzoate, methyl 4- dimethylaminobenzoate, methyl O-benzoylbenzoate, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-hydroxy-2-methyl-1-phenylpropan- 1-one, 2-isopropylthioxanthone, dibenzosuberone, 2,4,6- trimethylbenzoyldiphenylphosphine oxide, and bisacyclophosphine oxide.

[0036] Examples of suitable benzophenone photoinitiators include 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1,4,4-(2-hydroxyethoxy)phenyl]-2-methyl-1- -dimethoxy- -phenylacetophenone, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl) phenyl]-1-butanone, and 2-methyl-1-[4-(methylthio)phenyl]-2-(4- morpholinyl)-1-propanone.

[0037] Examples of suitable oxime photoinitiators include(hydroxyimino)cyclohexane, 1-[4-(phenylthio)phenyl]-octane-1,2-dione-2-(O- benzoyloxime), 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-ethanone-1-(O- acetyloxime), trichloromethyl-triazine derivatives), 4-(4-methoxystyryl)-2,6- trichloromethyl-1,3,5-triazine), 4-(4-methoxyphenyl)-2,6-trichloromethyl-1,3,5-triazine, -aminoketone (1-(4-morpholinophenyl)-2-dimethylamino-2-benzyl-butan-1-one).

[0038] Examples of suitable phosphine oxide photoinitiators include diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide (TPO) and phenylbis(2,4,6-trimethyl benzoyl) phosphine oxide (BAPO).

[0039] Other examples of suitable UV photoinitiators include the Irgacure™products from BASF; for example, the products Irgacure™ 184, Irgacure™ 500,Irgacure™ 1173, Irgacure™ 2959, Irgacure™ 745, Irgacure™ 651, Irgacure™ 369,Irgacure™ 907, Irgacure™ 1000, Irgacure™ 1300, Irgacure™ 819, Irgacure™819DW, Irgacure™ 2022, Irgacure™ 2100, Irgacure™ 784, or Irgacure™ 250; inaddition, the Irgacure™ products from BASF can be used; for example the productsIrgacure™ MBF, Darocur™ 1173, Darocur™ TPO, Darocur™ 4265.

[0040] A UV photoinitiator can comprise, for example, 2,2-dimethoxy-1,2-diphenylethan-1-one (Irgacure® 651, Ciba Specialty Chemicals), 2,4,6- trimethylbenzoyl-diphenyl-phosphineoxide (Darocur® TPO, Ciba Specialty Chemicals), or a combination thereof.

[0041] Other examples of suitable photoinitiators include Darocur® TPO(available from Ciba Specialty Chemicals), Lucirin® TPO (available from BASF), Speedcure® TPO (available from Lambson), Irgacure® TPO (available from Ciba Specialty Chemicals, and Omnirad® (available from IGM Resins), or combinations of any of the foregoing.

[0042] Compositions provided by the present disclosure can comprise from0.05 wt % to 5 wt %, from 0.1 wt % to 4.0 wt %, from 0.25 wt % to 3.0 wt %, or from 0.5 wt % to 1.5 wt % of a photoinitiator or combination of photoinitiators, where wt % is based on the total weight of the polymerizable composition.

[0043] Polymerizable compositions provided by the present disclosure cancomprise a polymerization moderator or a combination of polymerization moderators. A polymerization moderator can minimize the formation of any distortions or defects, e.g., striations and or cracks / fissures, in polymerizates that may be obtained from the polymerizable compositions of the present invention. Examples of suitable polymerization moderators include dilauryl thiodipropionate, 1-isopropyl-4-methyl-1,4-cyclohexadiene ( -terpinene); 1-isopropyl-4-methyl-1,3-cyclohexadiene ( -terpinene);1-methyl-4-(propan-2-ylidene)cyclohex-1-ene, (terpinolene); and -methyl styrene dimer, 1,1-diphenylethylene, cis-1,2-diphenylethylene, 3,7,7- trimethylbicyclo[4.1.0]hept-3-ene (3-carene), 4-isopropenyl-1-methylcyclohexene(dipentene), (S)-(+4-isopropenyl-1-methylcyclohexene ((S)-limonene), 2,6-dimethyl- 2,4,6-octatriene, 4-tert-butylpyrocatechol, triphenylmethane, or combinations of any of the foregoing.

[0044] A polymerization moderator can comprise 1-isopropyl-4-methyl-1,4-cyclohexadiene; 1-isopropyl-4-methyl-1,3-cyclohexadiene; 1-methyl-4-(propan-2-ylidene)cyclohex-1-ene; 2,6-dimethyl-2,4,6- -methyl styrene dimer, or acombination of any of the for -methyl styrene dimer refers to apolymerization moderator such as 2,4-diphenyl-4-methyl-1-pentene, and optionally at least one of 2,4-diphenyl-4-methyl-2-pentene and / or 2-phenyl-1-propene (which is -methyl styrene). With -methyl styrene dimer polymerization moderator includes 90 to 93 percent by weight of 2,4-diphenyl- 4-methyl-1-pentene, 6 to 8 percent by weight of 2,4-diphenyl-4-methyl-2-pentene, and 0.25 to 0.75 percent by weight of 2-phenyl-1-propene, the percent weights in each -methyl styrene dimer. A composition cancomprise, for example, from 0.01 to 15 percent by weight, or from 0.1 to 8 percent by weight, or from 0.3 to 5 percent by weight of a polymerization moderator, wherein percent by weight is based on the total weight of the composition.

[0045] The polymerizable compositions of the present disclosure may besubstantially free, essentially free, or completely free of isocyanate-functional compounds. As used herein, the terms “substantially free” means that a composition contains less than 1000 parts per million (ppm) of a certain component such as apolyisocyanate, “essentially free” means that the composition contains less than 100ppm of a certain component such as such as a polyisocyanate, and “completely free”means that the composition contains less than 20 parts per billion (ppb) of a certaincomponent.

[0046] The present disclosure is further drawn to polymerizates formed from thepolymerizable composition described above, and articles formed therefrom. Articles include, for example, optical articles such as a transparency; a glazing; a tinted or untinted lens; a plano or prescription lens; a sport mask; a face shield; a componentfor augmented reality, virtual reality, mixed reality, or smart eyewear; or goggles. Sucharticles typically demonstrate a refractive index (RI) of at least 1.51, or at least 1.55, or at least 1.60, or at least 1.63, or at least 1.66. In certain examples, a free radical- polymerizable compound as described above may be combined with monomers thattypically yield a polymerizate with a lower RI, and after polymerization produce a polymerizate with a higher RI such as at least 1.55, or at least 1.60, or at least 1.63. RI values may be measured at a wavelength of 543 nm using a prism coupling refractometer, such as a Metricon Model 2010 / M Prism Coupler equipped withmonochromatic light sources at 453, 543 and 633 nm, and corrected for temperature.

[0047] The reactive components of the polymerizable composition as describedabove may be reacted together via free-radical polymerization using techniquesknown in the art to yield a polymerizate, as further demonstrated in the Examplesbelow. A curing agent; i. e., crosslinking agent, is unnecessary.

[0048] Articles can be fabricated with polymerizable compositions provided bythe present disclosure using any suitable methods such as by casting, molding, and / or additive manufacturing such as stereolithography, digital light processing (DLP),continuous liquid interface production (CLIP), volumetric printing or material jetting..

[0049] In an example of preparing a molded polymerizate, the aforementionedpolymerizable composition may be introduced, usually by injection, into a mold of anydesired shape for a time to form a polymerizate. The reaction mixture is held in themold and typically subjected, as known in the art, to an elevated temperature and / oractinic radiation for a time sufficient to polymerize the reaction mixture and form amolded optical article. For example, the reaction mixture may be subjected to a temperature of 80° to 125°C, such as 100°C. The reaction mixture may be exposed toactinic radiation having a wavelength of 200 to 45 nm. The mold may have any shapedesired for the final product. It is typically a lens mold; often a mold for an ophthalmiclens. The molded article may then be released from the mold. Alternatively, thereaction mixture, which can be optionally degassed, can be introduced, usually by injection, into a mold. The cure cycle can vary depending on the reactivity and molarratio of the reactants, and the presence of catalyst(s). The cure cycle can last over aperiod of from 0.5 hours to 120 hours; such as from 5 hours to 72 hours.

[0050] The present disclosure is further drawn to the following aspects:1. A free radical-polymerizable compound comprising:(a) a thio(meth)acrylate functional group;(b) an aromatic group;(c) a thioketal and / or thioacetal group directly bonded to the aromatic group(b); and(d) a thioether functional linking group directly bonded to thethio(meth)acrylate functional group and the thioketal and / or thioacetal group.2. The free radical-polymerizable compound of aspect 1, wherein thecompound comprises 1 to 6 thio(meth)acrylate functional groups (a).3. The free radical-polymerizable compound of any preceding aspect,wherein the compound comprises 1 to 4 thio(meth)acrylate functional groups (a).4. The free radical-polymerizable compound of any preceding aspect,wherein the compound comprises 2 to 6 thio(meth)acrylate functional groups (a).5. The free radical-polymerizable compound of any preceding aspect,wherein the compound comprises 2 to 4 thio(meth)acrylate functional groups (a).6. The free radical-polymerizable compound of any preceding aspect,wherein the compound comprises 1 to 4 thioketal groups (c).7. The free radical-polymerizable compound of any preceding aspect,wherein the compound comprises 1 to 3 thioketal groups (c).8. The free radical-polymerizable compound of any preceding aspect,wherein the compound comprises 1 or 2 thioketal groups (c).9. The free radical-polymerizable compound of any preceding aspect,wherein the thioketal functional group (c) is derived from an aromatic ketone comprising 2-fluorenone, 9-fluorenone, 2-halo-9-fluorenone, 4-halo-9-fluorenone, 1,4- dihalo-9-fluorenone, 2,7-dihalo-9-fluorenone, 9-fluorenone-2-aldehyde, 9-fluorenone- 4-aldehyde, 9-fluorenone-2,7-dialdehyde, benzophenone, 4,4’dihalobenzophenone, and / or anthraquinone.10. The free radical-polymerizable compound of any preceding aspect,the compound comprises 1 to 4 thioacetal functional groups (c).11. The free radical-polymerizable compound of any preceding aspect,wherein the compound comprises 1 to 3 thioacetal functional groups (c).12. The free radical-polymerizable compound of any preceding aspect,wherein the compound comprises 1 or 2 thioacetal functional groups (c).13. The free radical-polymerizable compound of any preceding aspect,wherein the thioacetal functional group (c) is derived from an aromatic aldehyde comprising benzene-1,2-dicarbaldehyde, benzene-1,3-dicarbaldehyde, benzene-1,4- dicarbaldehyde, 9-fluorenone-2-aldehyde, 9-fluorenone-4-aldehyde, and / or 9- fluorenone-2,7-dialdehyde.14. The free radical-polymerizable compound of any preceding aspect,wherein the thioether functional linking group (d) is derived from a thioether functional polythiol.15. The free radical-polymerizable compound of aspect 14, wherein thethioether functional polythiol comprises bis-(2-mercaptoethyl) sulfide (DMDS), 1,4- Dithiane-2,5-dimethanethiol, 2,3-Bis((2-mercaptoethyl)thio)-1-propanethiol, and / or 4,8-Bis(mercaptomethyl)-1,11-dimercapto-o-3,6,9-trithiaundecane.16. The free radical polymerizable compound of aspect 15, wherein thethioether functional polythiol further comprises:(i) a polythiol according to Formula (II):H S n S wherein each n is(ii) a polythiol according to Formula (III):H S n S H S S n S S wherein each n(iii) a polythiol according to Formula (IV): RR'S S wherein R17. A polymerizable composition comprising the free radical-polymerizablecompound of any preceding aspect.18. The polymerizable composition of aspect 17, wherein the free radical-polymerizable compound is present in the composition in an amount of 5 to 100 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.19. The polymerizable composition of any of aspects 17 to 18, wherein thefree radical-polymerizable compound is present in the composition in an amount of 5 to 99 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.20. The polymerizable composition of any of aspects 17 to 19, wherein thefree radical-polymerizable compound is present in the composition in an amount of 5 to 95 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.21. The polymerizable composition of any of aspects 17 to 20, wherein thefree radical-polymerizable compound is present in the composition in an amount of 5to 80 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.22. The polymerizable composition of any of aspects 17 to 21, wherein thefree radical-polymerizable compound is present in the composition in an amount of 5 to 70 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.23. The polymerizable composition of any of aspects 17 to 22, wherein thefree radical-polymerizable compound is present in the composition in an amount of 5 to 60 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.24. The polymerizable composition of any of aspects 17 to 23, wherein thefree radical-polymerizable compound is present in the composition in an amount of 10 to 100 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.25. The polymerizable composition of any of aspects 17 to 24, wherein thefree radical-polymerizable compound is present in the composition in an amount of 10 to 99 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.26. The polymerizable composition of any of aspects 17 to 25, wherein thefree radical-polymerizable compound is present in the composition in an amount of 10 to 95 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.27. The polymerizable composition of any of aspects 17 to 26, wherein thefree radical-polymerizable compound is present in the composition in an amount of 10 to 80 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.28. The polymerizable composition of any of aspects 17 to 27, wherein thefree radical-polymerizable compound is present in the composition in an amount of 10 to 70 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.29. The polymerizable composition of any of aspects 17 to 28, wherein thefree radical-polymerizable compound is present in the composition in an amount of 10 to 60 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.30. The polymerizable composition of any of aspects 17 to 29, wherein thefree radical-polymerizable compound is present in the composition in an amount of 25 to 100 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.31. The polymerizable composition of any of aspects 17 to 30, wherein thefree radical-polymerizable compound is present in the composition in an amount of 25 to 99 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.32. The polymerizable composition of any of aspects 17 to 31, wherein thefree radical-polymerizable compound is present in the composition in an amount of 25 to 95 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.33. The polymerizable composition of any of aspects 17 to 32, wherein thefree radical-polymerizable compound is present in the composition in an amount of 25 to 80 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.34. The polymerizable composition of any of aspects 17 to 33, wherein thefree radical-polymerizable compound is present in the composition in an amount of 25to 70 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.35. The polymerizable composition of any of aspects 17 to 34, wherein thefree radical-polymerizable compound is present in the composition in an amount of 25 to 60 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.36. The polymerizable composition of any of aspects 17 to 35, wherein thefree radical-polymerizable compound is present in the composition in an amount of 35 to 100 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.37. The polymerizable composition of any of aspects 17 to 36, wherein thefree radical-polymerizable compound is present in the composition in an amount of 35 to 99 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.38. The polymerizable composition of any of aspects 17 to 37, wherein thefree radical-polymerizable compound is present in the composition in an amount of 35 to 95 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.39. The polymerizable composition of any of aspects 17 to 38, wherein thefree radical-polymerizable compound is present in the composition in an amount of 35 to 80 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.40. The polymerizable composition of any of aspects 17 to 39, wherein thefree radical-polymerizable compound is present in the composition in an amount of 35 to 70 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.41. The polymerizable composition of any of aspects 17 to 40, wherein thefree radical-polymerizable compound is present in the composition in an amount of 35 to 60 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.42. The polymerizable composition of any of aspects 17 to 41, wherein thefree radical-polymerizable compound is present in the composition in an amount of 50 to 100 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.43. The polymerizable composition of any of aspects 17 to 42, wherein thefree radical-polymerizable compound is present in the composition in an amount of 50 to 99 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.44. The polymerizable composition of any of aspects 17 to 43, wherein thefree radical-polymerizable compound is present in the composition in an amount of 50 to 95 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.45. The polymerizable composition of any of aspects 17 to 44, wherein thefree radical-polymerizable compound is present in the composition in an amount of 50 to 80 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.46. The polymerizable composition of any of aspects 17 to 45, wherein thefree radical-polymerizable compound is present in the composition in an amount of 50 to 70 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.47. The polymerizable composition of any of aspects 17 to 46, wherein thefree radical-polymerizable compound is present in the composition in an amount of 50to 60 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.48. The polymerizable composition of any of aspects 17 to 47, furthercomprising 2,5-bis(methacryloylthiomethyl)1,4-dithiane, 2-ethyl-2- ((meth)acryloylthiomethyl)-1,3-bis[(meth)acryloylthio]propane, 1,2,3- tris[(meth)acryloylthio]propane, 2,2-bis[(meth)acryloylthiomethyl]-1,3- bis[(meth)acryloylthio]propane, 4-(meth)acryloylthiomethyl-3,6-dithia-1,8- bis[(meth)acryloylthio]octane, 1,3-bis[(meth)acryloylthio]-2- (meth)acryloyloxypropane, 1-(meth)acryloylthio-2,3-bis[(meth)acryloyloxy]propane, 1,2-bis[(meth)acryloylthio]-3-(meth)acryloyloxypropane, 7-(meth)acryloyloxymethyl- 3,6,9,12-tetrathia-1,14-bis[(meth)acryloylthio]tetradecane, 7-[2- (meth)acryloyloxyethyl]-3,6,8,11-tetrathia-1,13-bis[(meth)acryloylthio]tridecane, 4,8- bis[(meth)acryloylthiomethyl]-3,6,9-trithia-1,11-bis[(meth)acryloylthio]undecane, and / or regioisomers of 4,8-bis[(meth)acryloylthiomethyl]-3,6,9-trithia-1,11- bis[(meth)acryloylthio]undecane.49. An article, such as an optical article, comprising a polymerizate formedfrom the polymerizable composition of any of aspects 17 to 48.50. The article of aspect 49, wherein said article is an optical articlecomprising a transparency; a glazing; a tinted or untinted lens; a plano or prescription lens; a sport mask; a face shield; a component for augmented reality, virtual reality,mixed reality, or smart eyewear; or goggles.51. The article of aspect 49 or 50, wherein the article demonstrates arefractive index (RI) of at least 1.51, measured at a wavelength of 543 nm using a prism coupling refractometer.52. The article of any of aspects 49 to 51, wherein the article demonstratesa refractive index (RI) of at least 1.55, measured at a wavelength of 543 nm using a prism coupling refractometer.53. The article of any of aspects 49 to 52, wherein the article demonstratesa refractive index (RI) of at least 1.60, measured at a wavelength of 543 nm using a prism coupling refractometer.54. The article of any of aspects 49 to 5534, wherein the articledemonstrates a refractive index (RI) of at least 1.66, measured at a wavelength of 543 nm using a prism coupling refractometer.55. A free radical-polymerizable compound comprising:(a) a thio(meth)acrylate functional group;(b) an aromatic group;(c) a thioketal and / or thioacetal group directly bonded to thearomatic group (b); and(d) a thioether functional linking group between the thio(meth)acrylatefunctional group and the thioketal and / or thioacetal group, wherein the free radical- polymerizable compound has a structure according to Formula (V): OX Ar Owherein X comprises H, an alkyl group or an aryl group, Ar comprises an aromatic group; or X and Ar together form a fused ring structure.

[0051] The following working Examples are intended to further describe anddemonstrate the compositions, polymerizates, and optical articles described herein. It is understood that the disclosure of this specification is not necessarily limited to the examples described in this section. Components that are mentioned elsewhere in the specification as suitable alternative materials for use, but which are not demonstrated in the working Examples below, are expected to provide results comparable to theirdemonstrated counterparts. Unless otherwise indicated, all parts are by weight.EXAMPLESPart 1. Synthesis of thiol-functional thioketal intermediates

[0052] For each example the components of Charge 1, as indicated in Table 1,were added to a flask equipped with an agitator, nitrogen inlet, thermocouple and reflux condenser. The mixture was stirred and heated to 40°C under nitrogen atmosphere. The acid catalyst of Charge 2 was added in two portions while maintaining a temperature of 40°C. The reaction mixtures of Examples 1, 2, and 4 were then heated to 70 °C and held at this temperature for 4 hours, while the reaction mixture of Example 3 was held at 40 °C for additional hour and then raised to 70 °C and held for 4 hours. The reaction mixtures, which became hazy, were then placed under vacuum for 4 hours at 70 °C for water removal.

[0053] Once the solution cooled to 25°C, ethyl acetate was added. The organiclayer was collected and washed with 10% NaOH and then saturated sodium chloride solution twice. The organic solution was concentrated by vacuum distillation, then filtered through a silica gel plug equipped with a 0.45 µm nylon syringe filter to provide a product containing a mixture comprising thiol-functional thioketal and thiol functional byproducts. The thiol equivalent weight of the product mixture was determined and reported in Table 1 below.

[0054] The thiol equivalent of each product mixture was determined by titrationwith an iodine solution using a Metrohm 865 Dosimat plus with a 30mL dosing burette. A sample (approximately 0.01 g) of the product was combined with 30 mL of toluene / 2- propanol (60 / 40wt%) and stirred at room temperature until the sample was dissolved. While stirring, the solution was titrated with 0.1 N iodine solution until a uniform light- yellow color was obtained. The thiol equivalent weight was calculated using Equation 1 below. Equation 1. mass sample (g) x 1000 mL / Lvolume titrant (mL) x 0.1N titrant Table 1: Synthesis of thio-ketal Example 1 Example 2 Example 3 Example 4 )Charge 19-Fluorenone 20.0 (0.111) 30.0 (0.166) 30.0 (0.172)

[0055] For each example, the thioketal mixture prepared in Part 1 was usedwithout further purification. The measured thiol equivalent weight was used to determine the amount of methacrylic anhydride required to yield a 1:1 equivalent ratio.For each example in Table 2, the components of Charge 1 were added to a reactor,stirred, then cooled to 0 – 5 °C under a nitrogen atmosphere. Methacrylic anhydrideof Charge 2 was added slowly to the solution while maintaining temperature range of between 0 °C and 5 °C.

[0056] Charge 3 was then added dropwise while maintaining a reactiontemperature range of 0 to 5 °C.After the sodium hydroxide solution addition, the reaction mixture was warmed to 25 °C and held for an additional 3 hours. The organic layer from the reaction mixture was collected and washed sequentially with water, then saturated sodium bicarbonate solution, and finally a saturated sodium chloride solution. The organic layer was then concentrated to dryness by vacuum distillation to obtain a viscous liquid, which was filtered through to a 0.45-micron filter to provide a product mixture comprising thiomethacrylate-functional thioketals. Table 2: Preparation of thiomethacrylate-functional thiolsComponents Example 5 Example 6 Example 7 Example 8Product of Example 4- - - 29 (1.0)

[0057] Bis(2-mercaptoethyl)sulfide was added dropwise to a solution of 1.03equivalent of sodium hydroxide (NaOH) in water, with stirring, under an atmosphere of nitrogen.

[0058] The resulting solution was then added dropwise to a solution of 1.0equivalent of methacryloyl chloride in dichloromethane, with mixing and cooling to a reaction temperature of 0-5 °C, under an atmosphere of nitrogen. After mixing at room temperature for an additional 3 hours, the organic layer was collected and washed three times, as follows: (i) water, (ii) saturated sodium bicarbonate solution, and (iii) saturated sodium chloride solution. A stabilizer package consisting of 250 ppm of 4- methoxyphenol plus 250 ppm of 4-tert-butylcatechol was added, volatiles were removed via vacuum distillation, and the product was filtered to yield the corresponding difunctional thiomethacrylate. Table 3: Components of comparative thiomethacrylate material CE-9 CE- 9Reactants ( iv)Part 4. Lens Casting

[0059] Each polymerizable composition from Examples 5 to 8 and ComparativeExample CE-9 was used to prepare a corresponding cast lens ("polymerizate") according to the following procedure.

[0060] Each polymerizable composition was transferred to a glass vessel, towhich 0.1 percent by weight of Irgacure 819 photo-initiator (available from BASF) was added. The resulting mixture was stirred at 50°C until homogeneous. The polymerizable composition including the photo-initiator was filtered and dispensed into a mold consisting of two pieces of UV-transparent glass separated by a plastic gasket (spacer) to control lens thickness. The internal dimensions of the mold cavity were designed to yield a final cured piece having thickness of 3.5 mm. The filled molds were exposed to UV light via a UV irradiation device from LESCO Incorporated fitted with a Fusion UV Curing Systems F-300 focused beam microwave powered lamp, equipped with a D-bulb in which 64 percent of the emitted energy was between 300 and 400 nm. The UV intensities and dosage energies used are shown in Table 4. Table 4: UV Curing ParametersUVC UVC UVB UVA UVV (280-320 (320-395 (395-455 evice.

[0061] A line speed of 1.5 feet per minute (ft / min) (0.45 meters per minute(m / min)) was used, and each filled mold assembly was passed under the UV light three times. Between passes, the mold was turned over to expose the opposite side to the UV light source. After exposing the polymerizable composition to UV radiation, a disk-shaped lens was recovered from the mold assembly and then heated at 100 degrees centigrade for 1 hour. It was then used to measure physical properties. Part 5. Properties

[0062] Refractive index was measured using a Metricon Model 2010 / M PrismCoupler equipped with monochromatic light sources at 453, 543 and 633 nm and corrected for temperature. Abbe number was calculated from the refractive index values according to the below equations (2) and (3) where VD and Ve are the Abbevalues with respect to the Fraunhofer d- and green mercury E-lines respectively, andnd, nF, nC, ne, nF’ and nC’ are the refractive indices of the material at the FraunhoferD-, F-, C- lines, green mercury E-line, blue and red cadmium lines, respectively.Refractive indices at wavelengths not directly measured were calculated from a best fit of the empirical data to Cauchy’s equation. Results are shown in Table 4. Equation (2): =Equation (3): =Table 5:Lens prepared Lens Lens Lens prepared prepared prepared Lens preparedexhibit higher refractive index than the comparative example prepared from bis(2- mercaptoethyl)sulfide while maintaining good Abbe values.

[0064] Whereas particular examples of this disclosure have been describedabove for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present disclosure may be made without departing therefrom as defined in the appended claims. Although various examples of the disclosure have been described in terms of "comprising", embodiments consisting essentially of or consisting of are also within the scope of the present disclosure.

Claims

What is claimed is:

1. A free radical-polymerizable compound comprising:(a) a thio(meth)acrylate functional group;(b) an aromatic group;(c) a thioketal and / or thioacetal group directly bonded to the aromatic group(b); and (d) a thioether functional linking group directly bonded to thethio(meth)acrylate functional group and the thioketal and / or thioacetal group.

2. The free radical-polymerizable compound of claim 1, wherein the compoundcomprises 1 to 6 thio(meth)acrylate functional groups (a).

3. The free radical-polymerizable compound of claim 1 or 2, wherein thecompound comprises 1 to 4 thioketal groups (c).

4. The free radical-polymerizable compound of claim 3, wherein the thioketalgroup (c) is derived from an aromatic ketone comprising 2-fluorenone, 9-fluorenone, 2-halo-9-fluorenone, 4-halo-9-fluorenone, 1,4-dihalo-9-fluorenone, 2,7-dihalo-9- fluorenone, 9-fluorenone-2-aldehyde, 9-fluorenone-4-aldehyde, 9-fluorenone-2,7- dialdehyde, benzophenone, 4,4’dihalobenzophenone, and / or anthraquinone.

5. The free radical-polymerizable compound of any of claims 1 to 3, wherein thecompound comprises 1 to 4 thioacetal groups (c).

6. The free radical-polymerizable compound of claim 5, wherein the thioacetalgroup (c) is derived from an aromatic aldehyde comprising benzene-1,2- dicarbaldehyde, benzene-1,3-dicarbaldehyde, benzene-1,4-dicarbaldehyde, 9- fluorenone-2-aldehyde, 9-fluorenone-4-aldehyde, and / or 9-fluorenone-2,7- dialdehyde.

7. The free radical-polymerizable compound of any of claims 1 to 6, wherein thethioether functional linking group (d) is derived from a thioether functional polythiol.

8. The free radical-polymerizable compound of claim 7, wherein the thioetherfunctional polythiol comprises bis-(2-mercaptoethyl) sulfide (DMDS), 1,4-Dithiane-2,5-dimethanethiol, 2,3-Bis((2-mercaptoethyl)thio)-1-propanethiol, and / or 4,8-Bis(mercaptomethyl)-1,11-dimercapto-o-3,6,9-trithiaundecane.

9. The free radical polymerizable compound of claim 8, wherein the thioetherfunctional polythiol further comprises:(i) a polythiol according to Formula (II):H S n S wherein each n is(ii) a polythiol :H S n S H S S nwherein each n is independently from 2 to 4, and m is 1 or 2; and / or (iii) a polythiol according to Formula (IV): RR'wherein R10. The free radical-polymerizable compound of claim 1, wherein the free radical-polymerizable compound has a structure according to Formula (V):O X Ar OS Saromaticgroup; or X and Ar together form a fused ring structure.

11. A polymerizable composition comprising the free radical-polymerizablecompound of any of claims 1 to 10.

12. The polymerizable composition of claim 11, wherein the free radical-polymerizable compound is present in the composition in an amount of 5 to 100 percent by weight, based on the total weight of polymerizable components on the polymerizable composition.

13. The polymerizable composition of claim 11 or 12, further comprising 2,5-bis(methacryloylthiomethyl)1,4-dithiane, 2-ethyl-2-((meth)acryloylthiomethyl)-1,3- bis[(meth)acryloylthio]propane, 1,2,3-tris[(meth)acryloylthio]propane, 2,2- bis[(meth)acryloylthiomethyl]-1,3-bis[(meth)acryloylthio]propane, 4- (meth)acryloylthiomethyl-3,6-dithia-1,8-bis[(meth)acryloylthio]octane, 1,3- bis[(meth)acryloylthio]-2-(meth)acryloyloxypropane, 1-(meth)acryloylthio-2,3- bis[(meth)acryloyloxy]propane, 1,2-bis[(meth)acryloylthio]-3- (meth)acryloyloxypropane, 7-(meth)acryloyloxymethyl-3,6,9,12-tetrathia-1,14- bis[(meth)acryloylthio]tetradecane, 7-[2-(meth)acryloyloxyethyl]-3,6,8,11-tetrathia- 1,13-bis[(meth)acryloylthio]tridecane, 4,8-bis[(meth)acryloylthiomethyl]-3,6,9-trithia-1,11-bis[(meth)acryloylthio]undecane, and / or regioisomers of 4,8-bis[(meth)acryloylthiomethyl]-3,6,9-trithia-1,11-bis[(meth)acryloylthio]undecane.

14. An article comprising a polymerizate formed from the polymerizablecomposition of any of claims 11 to 13.

15. The article of claim 14, wherein said article is an optical article comprising atransparency; a glazing; a tinted or untinted lens; a plano or prescription lens; a sportmask; a face shield; a component for augmented reality, virtual reality, mixed reality, or smart eyewear; or goggles.

16. The article of claim 14 or 15, wherein the article demonstrates a refractive index(RI) of at least 1.51, measured at a wavelength of 543 nm using a prism coupling refractometer.

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