Synthesis and characterization of poly(isobutylene‐co‐isoprene)‐derived macro‐monomers

Allylic halide displacement from brominated poly(isobutylene‐co‐isoprene) (BIIR) by carboxylate nucleophiles is used to prepare elastomer derivatives containing pendant polymerizable functionality. These solvent‐borne substitutions are conducted under homogeneous and phase‐transfer catalyzed reaction conditions to synthesize acrylate and vinylbenzoate esters in high yield. The resulting macro‐monomer derivatives are shown to crosslink efficiently with peroxide initiation to give high modulus, thermoset products that cannot otherwise be accessed from isobutylene‐rich elastomers. The extent of cure, as measured by the storage modulus of the vulcanizate, scales with RCH=CH₂ content, and can be extended by co‐oligomerization of pendant unsaturation with that contained within multifunctional coagents. An alternate approach involving the introduction of pendant sulfonyl azide functionality is described, wherein thermal decomposition to nitrene intermediates supports an efficient crosslinking process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Temperature‐sensitive hydrogel microspheres formed by liquid–liquid phase transitions of aqueous solutions of poly(N,N‐dimethylacrylamide‐co‐allyl methacrylate)

Poly(N,N‐dimethylacrylamide‐co‐allyl methacrylate) (DMA‐co‐AMA) copolymers were prepared by the copolymerization of N,N‐dimethylacrylamide with allyl methacrylate (AMA). The methacryloyl group of AMA reacted preferentially, and this resulted in pendant allyl groups along the copolymer chains. Aqueous solutions of these DMA‐co‐AMA copolymers were thermoresponsive and showed liquid–liquid phase transitions at temperatures that depended on the AMA content. Hydrogel microspheres were prepared from these thermally phase‐separated liquid microdroplets by the free‐radical crosslinking of the pendant allyl groups. The morphologies of the resulting thermoresponsive microspheres as a function of the reaction temperature and the amount of the initiator were examined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1641–1648, 2005     

Crosslinking photocopolymerization of acrylic acid (and N‐vinylpyrrolidone) with triethyleneglycol dimethacrylate initiated by camphorquinone/ethyl‐4‐dimethylaminobenzoate

In this article, we report the camphorquinone/amine visible‐light‐induced photocopolymerization of monofunctional acrylic acid (AA), N‐vinylpyrrolidone (NVP), or both with difunctional triethyleneglycol dimethacrylate (TEGDMA) monomers followed by the crosslinking of pendant double‐bond groups of the resulting homopolymers and copolymers. Our primary objective was to study the photocopolymerizability of various mixtures of AA, NVP, and TEGDMA compositions at different molar ratios in air. The photocopolymerization of AA with TEGDMA occurred with the formation of two peaks at different rates of polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 876–886, 2000     

Peroxide‐initiated chemical modification of poly(isobutylene‐co‐isoprene): H‐atom transfer yields and regioselectivity

The yield and regioselectivity of H‐atom abstraction by cumyloxy radicals from poly(isobutylene‐co‐isoprene) (IIR) are quantified and discussed in the context of cross‐linking/degradation outcomes and vinyltriethoxysilane (VTEOS) graft yields. Studies of IIR materials with different isoprene contents show that H‐atom abstraction from the allylic functionality provided by isoprene mers is responsible for the heightened H‐atom transfer reactivity of IIR relative to poly(isobutylene). Differences in the reactivity of allylic and alkyl macroradical intermediates makes high isoprene IIR materials less prone to peroxide‐initiated chain scission, but less responsive to VTEOS grafting formulations. Improved knowledge of H‐atom transfer reactivity is extended to a new approach for IIR cross‐linking involving acrylate‐functionalized nitroxyl chemistry. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3102–3109     

Synthesis and thermal crosslinking of benzophenone‐modified poly(dimethylsiloxane)s

Dihydridocarbonyltris(triphenylphosphine)ruthenium catalyzes the regiospecific anti‐Markovnikov addition of an ortho C? H bond of benzophenone across the C? C double bonds of α,ω‐bis(trimethylsilyloxy)copoly(dimethylsiloxane/vinylmethylsiloxane) (99:1), α,ω‐bis(vinyldimethylsilyloxy)poly(dimethylsiloxane), and 1,3‐divinyltetramethyldisiloxane to yield α,ω‐bis(trimethylsilyloxy)copoly[dimethylsiloxane/2‐(2′‐benzophenonyl)ethylmethylsiloxane]), α,ω‐bis[2‐(2′‐benzophenonyl)ethyldimethylsilyloxy]poly(dimethylsiloxane), and 1,3‐bis[2‐(2′‐benzophenonyl)ethyl]tetramethyldisiloxane, respectively. These materials have been characterized with ¹H, ¹³C, and ²⁹Si NMR and IR spectroscopy. Their molecular weight distributions have been determined by gel permeation chromatography. The thermal stability of the polymers has been measured by thermogravimetric analysis, and their glass‐transition temperatures (T_g's) have been determined by differential scanning calorimetry. The molecular weight distribution, thermal stability, and T_g's of the modified polysiloxanes are similar to those of the precursor polymers. The molecular weights of these materials can be significantly increased via heating to 300 °C for 1 h. This may be due to crosslinking, by pyrocondensation, of pendant anthracene groups, which are produced by the pyrolysis of the attached ortho‐alkyl benzophenones. UV spectroscopy of the pyrolysate of 1,3‐bis[2‐(2′‐benzophenonyl)ethyl]tetramethyldisiloxane has confirmed the presence of pendant anthracene groups. Thermal crosslinking by the pyrocondensation of pendant anthracene groups has been verified by the pyrolysis of α,ω‐bis(trimethylsilyloxy)copoly[dimethylsiloxane/2‐(9′‐anthracenyl)ethylmethylsiloxane] (97:3). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5514–5522, 2004     

Biodegradable polymers based on renewable resources. IX. Synthesis and degradation behavior of polycarbonates based on 1,4:3,6‐dianhydrohexitols and tartaric acid derivatives with pendant functional groups

Novel polycarbonates, with pendant functional groups, based on 1,4:3,6‐dianhydrohexitols and L ‐tartaric acid derivatives were synthesized. Solution polycondensations of 1,4:3,6‐dianhydro‐bis‐O‐(p‐nitrophenoxycarbonyl)hexitols and 2,3‐di‐O‐methyl‐L ‐threitol or 2,3‐O‐isopropylidene‐L ‐threitol afforded polycarbonates having pendant methoxy or isopropylidene groups, respectively, with number average molecular weight (M_n) values up to 3.6₁ × 10⁴. Subsequent acid‐catalyzed deprotection of isopropylidene groups gave well‐defined polycarbonates having pendant hydroxyl groups regularly distributed along the polymer chain. Differential scanning calorimetry (DSC) demonstrated that all the polycarbonates were amorphous with glass transition temperatures ranging from 57 to 98 °C. Degradability of the polycarbonates was assessed by hydrolysis test in phosphate buffer solution at 37 °C and by biochemical oxygen demand (BOD) measurements in an activated sludge at 25 °C. In both tests, the polycarbonates with pendant hydroxyl groups were degraded much faster than the polycarbonates with pendant methoxy and isopropylidene groups. It is noteworthy that degradation of the polycarbonates with pendant hydroxyl groups was remarkably fast. They were completely degraded within only 150 min in a phosphate buffer solution and their BOD‐biodegradability reached nearly 70% in an activated sludge after 28 days. The degradation behavior of the polycarbonates is discussed in terms of their chemical and physical properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3909–3919, 2005     

Effects of filler–polymer interactions on cold‐crystallization kinetics in crosslinked,silica‐filled polydimethylsiloxane/polydiphenylsiloxane copolymer melts

Crystallization in a series of variable crosslink density poly(dimethyl‐diphenyl)siloxanes random block copolymers reinforced through a mixture of precipitated and fumed silica fillers has been studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), nuclear magnetic resonance (NMR), and X‐ray diffraction (XRD). The silicone composite studied was composed of 94.6 mol % dimethoylsiloxane, 5.1 mol % diphenylsiloxane, and 0.3 mol % methyl‐vinyl siloxane (which formed crosslinking after peroxide cure). The polymer was filled with a mixture of 21.6 wt % fumed silica and 4.0 wt % precipitated silica previously treated with 6.8 wt % ethoxy‐end‐blocked siloxane processing aid. Molecular weight between crosslinks and filler–polymer interaction strength were modified by exposure to γ‐irradiation in either air or in vacuo. Isothermal DMA experiments illustrated that crystallization at ?85 °C occurred over a 1.8 hour period in silica‐filled systems and 2.2–2.6 hours in unfilled systems. The crystallization kinetics for irradiated samples were found to be dependent on crosslink density. Irradiation in vacuo resulted in faster overall crystallization rates compared to air irradiation for the same crosslink density, likely due to a reduction in the interaction between the polymer chains and the silica filler surface for samples irradiated in air. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1898–1906, 2006     

Novel thermotropic liquid crystalline‐cum‐photocrosslinkable polyvanillylidene alkyl/arylphosphate esters

A new class of linear unsaturated polyphosphate esters based on divanillylidene cyclohexanone possessing liquid crystalline‐cum‐photocrosslinkable properties have been synthesized from 2,6‐bis[n‐hydroxyalkyloxy(vanillylidene)]cyclohexanone [n = 6,8,10] with various alkyl/aryl phosphorodichloridates in chloroform at ambient temperature. The resultant polymers were characterized by intrinsic viscosity, FT‐IR, ¹H, ¹³C, and ³¹P‐NMR spectroscopy. All the polymers showed anisotropic behavior under hot stage optical polarized microscope (HOPM). The liquid crystalline textures of the polymers became more transparent with increasing spacer length. The thermal behavior of the polymers was studied by thermogravimetric analysis and differential scanning calorimetry. The T_g, T_m, and T_i of the polymers decreased with increasing flexible methylene chain. The photocrosslinking property of the polymer was investigated by UV light/UV spectroscopy; the crosslinking proceeds via 2π‐2π cycloaddition reactions of the divanillylidene exocyclic double bond of the polymer backbone. The pendant alkyloxy containing polymers show faster crosslinking than the pendant phenyloxy containing polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5215–5226, 2004     

Enhancing cationic ring‐opening photopolymerization of cycloaliphatic epoxides via dark cure and oxetanes

Due to the longevity of the cationic active centers, cationic ring‐opening photopolymerization can continue after illumination ceases. In addition, substantial reactivity enhancement for epoxides is realized through copolymerization with oxetanes. Here, the separate reactions of epoxide and oxetane moieties were resolved during illumination and subsequent dark cure via real‐time Raman spectroscopy. Using oxetane additives, reactivity and conversion of 3,4‐epoxycyclohexylmethyl‐3′,4′‐epoxycyclohexane carboxylate (EEC) were improved during illumination and subsequent dark cure through modulation of the initial formulation viscosity and selection of the oxetane secondary functional groups. The largest enhancement in reactivity occurred with secondary groups comprising either aliphatic chains with their flexibility or hydroxyls with their chain‐transfer capacity. In contrast, oxetanes containing UV‐absorbing phenyl rings reduced the initiation efficiency, and difunctional oxetanes suppressed overall conversion through additional crosslinking. Although bulk conversion was directly related to initial formulation viscosity, the impact of the oxetane secondary functional groups was greater. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1436–1445     

Sulfuration and reversion reactions of brominated poly(isobutylene‐co‐isoprene)

The sulfuration and reversion products of brominated poly(isobutylene‐co‐isoprene) (BIIR) were characterized through the use of a model compound, brominated 2,2,4,8,8‐pentamethyl‐4‐nonene (BPMN). The reaction of BPMN with S₈ produced bisallylic polysulfides of various ranks, yielding sulfur bromide intermediates that likely contributed to the rapid oxidation of allylic sulfides into thiophenes. Reductive cure reversion to pentamethylnonene was also observed in the latter stages of vulcanization. The reaction of 2,2′‐dithiobisbenzothiazole with BIIR and BPMN produced a stable adduct that reduced the concentration of allylic bromide available for vulcanization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1915–1926, 2003     

Synthesis and antibacterial activities of water‐soluble methacrylate polymers containing quaternary ammonium compounds

New water‐soluble methacrylate polymers with pendant quaternary ammonium (QA) groups were synthesized and used as antibacterial materials. The polymers with pendant QA groups were obtained by the reaction of the alkyl halide groups of a previously synthesized functional methacrylate homopolymer with various tertiary alkyl amines containing 12‐, 14‐, or 16‐carbon alkyl chains. The structures of the functional polymer and the polymers with QA groups were confirmed with Fourier transform infrared and ¹H and ¹³C NMR. The degree of conversion of alkyl halides to QA sites in each polymer was determined by ¹H NMR to be over 90% in all cases. The number‐average molecular weight and polydispersity of the functional polymer were determined by size exclusion chromatography to be 32,500 g/mol and 2.25, respectively. All polymers were thermally stable up to 180 °C according to thermogravimetric analysis. The antibacterial activities of the polymers with pendant QA groups against Staphylococcus aureus and Escherichia coli were determined with broth‐dilution and spread‐plate methods. All the polymers showed excellent antibacterial activities in the range of 32–256 μg/mL. The antibacterial activity against S. aureus increased with an increase in the alkyl chain length for the ammonium groups, whereas the antibacterial activity against E. coli decreased with increasing alkyl chain length. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5965–5973, 2006     

Synthesis of allyl end‐block functionalized poly(ε‐caprolactone)s and their facile post‐functionalization via thiol–ene reaction

A simple and facile strategy for the functionalization of commercial poly(ε‐caprolactone) diols (PCLs) with pendant functionalities at the polymer chain termini is described. Well‐defined allyl‐functionalized PCLs with varying numbers of allyl end‐block side‐groups were synthesized by cationic ring‐opening polymerization of allyl glycidyl ether using PCL diols as macroinitiators. Further functionalization of the allyl‐functionalized PCLs was realized via the UV‐initiated radical addition of a furan‐functionalized thiol to the pendant allyl functional groups, showing the suitability for post‐modification of the PCL materials. Changes in polymer structure as a result of varying the number of pendant functional units at the PCL chain termini were demonstrated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 928–939     

Synthesis and properties of ortho‐linked aromatic polyimides based on 1,2‐bis(4‐aminophenoxy)‐4‐tert‐butylbenzene

A bis(ether amine) containing the ortho‐substituted phenylene unit and pendant tert‐butyl group, 1,2‐bis(4‐aminophenoxy)‐4‐tert‐butylbenzene, was synthesized and used as a monomer to prepare polyimides with six commercial dianhydrides via a conventional two‐stage procedure. The intermediate poly(amic acid)s had inherent viscosities of 0.78–1.44 dL/g, and most of them could be thermally converted into transparent, flexible, and tough polyimide films. The inherent viscosities of the resulting polyimides were in the range of 0.46–0.87 dL/g. All polyimides were noncrystalline, and most of them showed excellent solubility in polar organic solvents. The glass‐transition temperatures of these polyimides were in the range of 222–259 °C in differential scanning calorimetry and 212–282 °C in thermomechanicl analysis. These polyimides showed no appreciable decomposition up to 500 °C in thermogravimetric analysis in air or nitrogen. A comparative study of the properties with the corresponding polyimides without pendant tert‐butyl groups derived from 1,2‐bis(4‐aminophenoxy)benzene is also presented. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1551–1559, 2000     

Allyl ethers as combined plasticizing and crosslinkable side groups in polycarbonate‐based polymer electrolytes for solid‐state Li batteries

Allyl ether‐functional polycarbonates, synthesized by organocatalytic ring‐opening polymerization of the six‐membered cyclic carbonate monomer 2‐allyloxymethyl‐2‐ethyltrimethylene carbonate, were used to prepare non‐polyether polymer electrolytes. UV‐crosslinking of the allyl side groups provided mechanically stable electrolytes with improved molecular flexibility—T_g below ?20 °C—and higher ionic conductivity—up to 4.3 × 10^?7 S/cm at 25 °C and 5.2 × 10^?6 S/cm at 60 °C—due to the plasticizing properties of the allyl ether side groups. The electrolyte function was additionally demonstrated in thin‐film Li battery cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2128–2135     

Pendant groups fine‐tuning thermal gelation of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) aqueous solution

Novel poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) (PCL‐PEG‐PCL) bearing pendant hydrophobic γ‐(carbamic acid benzyl ester) groups (PECB) and hydrophiphilic amino groups (PECN) were synthesized based on the functionalized comonomer γ‐(carbamic acid benzyl ester)‐ε‐caprolactone (CABCL). The thermal gelation behavior of the amphiphilic copolymer aqueous solutions was examined. The phase transition behavior could be finely tuned via the pendant groups, and an abnormal phenomenon occurred that the sol–gel transition temperature shifted to a higher temperature for PECB whereas a lower temperature for PECN. The micelles percolation was adopted to clarify the hydrogel mechanism, and the effect of the pendant groups on the micellization was further investigated in detail. The results demonstrated that the introduction of γ‐(carbamic acid benzyl ester) pendant groups significantly decreased the crystallinity of the copolymer micelles whereas amino pendant groups made the micelles easy to aggregate. Thus, the thermal gelation of PEG/PCL aqueous solution could be finely tuned by the pendant groups, and the pendant groups modified PEG/PCL hydrogels are expected to have great potential biomedical application. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2571–2581     

Photo‐induced thiol‐ene polysulfide‐crosslinked materials with tunable thermal and mechanical properties

Photo‐induced thiol‐ene crosslinked polymeric networks have been extensively explored in constructing a variety of new materials with enhanced mechanical properties for optical, biomedical, and sensing applications. Toward the broad applications, however, tunable mechanical properties are greatly desired. Here, an effective approach utilizing high‐molecular‐weight methacrylate copolymers having pendant thiol and vinyl groups (MCPsh and MCPenes) to modulate thermal and mechanical properties of photo‐induced thiol‐ene crosslinked materials is reported. The MCP copolymers are synthesized by an industrially friendly polymerization method, followed by post‐modification including either a facile coupling reaction or reductive cleavage. Upon UV irradiation, thiol‐ene reactive blends of MCPsh and MCPenes yield highly crosslinked materials through the formation of flexible sulfide linkages. These polysulfide‐crosslinked materials based on rigid MCP backbones exhibit enhanced mechanical properties. Further, their thermal and mechanical properties are tuned by modulating monomer compositions of MCPs as well as varying numbers of pendant SH or vinyl groups (i.e., extent of crosslinking densities). This approach is versatile and effective for development of high performance polymeric materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3060–3068     

Phosphoric acid‐doped imidazolium ionomers with enhanced stability for anhydrous proton‐exchange membrane applications

Phosphoric acid‐doped crosslinked proton‐conducting membranes with high anhydrous proton conductivity, and good chemical stability in phosphoric acid were synthesized and characterized. The synthetic procedure of the acid‐doped composite membranes mainly involves the in situ crosslinking of polymerizable monomer oils (styrene and acrylonitrile) and vinylimidazole, and followed by the sulfonation of pendant imidazole groups with butanesultone, and further doped with phosphoric acid. The resultant phosphoric acid‐doped composite electrolyte membranes are flexible and show high thermal stability and high‐proton conductivity up to the order of 10^?2 S cm^?1 at 160 °C under anhydrous conditions. The phosphoric acid uptake, swelling degree, and proton conductivity of the composite membranes increase with the vinylimidazole content. The resultant composite membranes also show good oxidative stability in Fenton's reagent (at 70 °C), and quite good chemical stability in phosphoric acid (at 160 °C). The properties of the prepared electrolyte membranes indicate their promising prospects in anhydrous proton‐exchange membrane applications. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 , 51, 1311–1317     

Chemical modification of poly(lactic acid) induced by thermal decomposition of N‐acetoxy‐phthalimide during extrusion

Chemical modification of poly(lactic acid) (PLA) with N‐acetoxy‐phthalimide (NAPI) was performed in the melt by reactive extrusion, without using any peroxide initiator. The aminyl and nitroxide radicals produced from the NAPI thermal degradation, were, respectively, used (a) to create PLA macroradicals, and (b) to functionalize the PLA samples through nitroxide radical coupling. Depending on the extrusion temperature and the initial NAPI concentration, grafting rates up to 0.24 mol % were measured, modifying the PLA optical properties. This study represents an original new way of modification of PLA without the use of conventional peroxide initiators. Indeed, the undesirable side reactions (PLA branching or crosslinking) usually observed when using peroxides to initiate the radical grafting of PLA were avoided when using NAPI. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 120–129     

Hydrolysis of 4‐acetoxystyrene polymers prepared by atom transfer radical polymerization

Hydrolysis of 4‐acetoxystyrene polymers prepared by atom transfer radical polymerization was carried out under various reaction conditions. It was found that hydrazinolysis of 4‐acetoxystyrene homopolymers, random and block copolymers with styrene in 1,4‐dioxane, afforded the corresponding narrow dispersed materials with phenolic groups which were substantially free from crosslinkages. Gel permeation chromatographic (GPC) analysis of these polymers revealed different extents of molecular weight distribution (MWD) broadening for the hydrolysis products for the different structures. On the other hand, by NaOH catalyzed deprotection, the 4‐acetoxystyrene polymers including triblock copolymer poly(4‐acetoxystyrene‐b‐isobutylene‐b‐4‐acetoxystyrene) suffered from some degrees of coupling or even gelation, except for poly(styrene‐b‐4‐acetoxystyrene‐b‐styrene) which also by this method could be conveniently converted to its phenolic product. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 627–633, 1999     

Thermal radical initiator derivatives based on O‐imino‐isourea: Synthesis,polymerization, and characterization

The new thermal radical initiators (TRIs) with linear and cyclic type groups based on derivatives of O‐imino‐isourea have been designed and synthesized. The radical polymerization property of the synthesized TRI derivatives as a radical initiator in n‐butyl acrylate was monitored by differential scanning calorimetry analysis. TRI derivatives with linear type groups, such as 3‐PenDCC, 3‐HexDCC, and 4‐HepDCC, showed peak temperatures (T_peak) of 80–84 °C, whereas those with cyclic type groups, such as C‐PenDCC, C‐HexDCC, and C‐HepDCC, exhibited a wide T_peak distribution in the 74–87 °C range. The polymerization efficiency using new TRIs in n‐butyl acrylate was elaborately identified from the molecular weights and conversion obtained using gel permeation chromatography analysis and NMR spectroscopy. To consider their possible application to automotive clearcoats, the real‐time evolution of the rheological properties of clearcoat resins during the crosslinking process with newly synthesized TRI derivatives was measured, confirming the different crosslinking kinetics of TRI derivatives in real thermal curing process. The results were found to be well correlated with data from the radical polymerization experiments of TRIs. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3593–3600.