Synthesis of well‐defined azide‐terminated poly(vinyl alcohol) and their subsequent modification via click chemistry

A new azide‐functionalized xanthate, S‐(4‐azidomethylbenzyl) O‐(2‐methoxyethyl) xanthate, was synthesized and used to mediate the reversible addition fragmentation chain transfer polymerization of vinyl acetate. The polymerization was demonstrated to be controlled, and well‐defined PVAc with α‐azide, ω‐xanthate groups were obtained, the xanthate groups of which were further removed by radical‐induced reduction with lauroyl peroxide in the presence of excess 2‐propanol. Hydrolysis of α‐azide‐terminated PVAc (N₃‐PVAc) led to the formation of the corresponding α‐azide‐terminated PVA (N₃‐PVA). Finally, end‐modification of N₃‐PVA by click chemistry with alkyne‐end‐capped poly(caprolactone) (A‐PCL), alkynyl‐mannose, and alkynyl‐pyrene was carried out to obtain a new block copolymer PCL‐b‐PVA, and two PVA with mannose or pyrene as the end functional groups. The polymers were characterized by gel permeation chromatography, ¹H NMR spectroscopy, and FTIR. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4494–4504, 2009     

Synthesis and characterization of star graft copolymers with asymmetric mixed “V‐shaped” side chains via “click” chemistry on a hyperbranched polyglycerol core

The star graft copolymers composed of hyperbranched polyglycerol (HPG) as core and well defined asymmetric mixed “V‐shaped” identical polystyrene (PS) and poly(tert‐butyl acrylate) as side chains were synthesized via the “click” chemistry. The V‐shaped side chain bearing a “clickable” alkyne group at the conjunction point of two blocks was first prepared through the combination of anionic polymerization of styrene (St) and atom transfer radical polymerization of tert‐butyl acrylate (tBA) monomer, and then “click” chemistry was conducted between the alkyne groups on the side chains and azide groups on HPG core. The obtained star graft copolymers and intermediates were characterized by gel permeation chromatography (GPC), GPC equipped with a multiangle laser‐light scattering detector (GPC‐MALLS), nuclear magnetic resonance spectroscopy and fourier transform infrared. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1308–1316, 2009     

Synthesis,characterization, and micellization of PCL‐g‐PEG copolymers by combination of ROP and “Click” chemistry via “Graft onto” method

Biodegradable and biocompatible PCL‐g‐PEG amphiphilic graft copolymers were prepared by combination of ROP and “click” chemistry via “graft onto” method under mild conditions. First, chloro‐functionalized poly(ε‐caprolactone) (PCL‐Cl) was synthesized by the ring‐opening copolymerization of ε‐caprolactone (CL) and α‐chloro‐ε‐caprolactone (CCL) employing scandium triflate as high‐efficient catalyst with near 100% monomer conversion. Second, the chloro groups of PCL‐Cl were quantitatively converted into azide form by NaN₃. Finally, copper(I)‐catalyzed cycloaddition reaction was carried out between azide‐functionalized PCL (PCL‐N₃) and alkyne‐terminated poly(ethylene glycol) (A‐PEG) to give PCL‐g‐PEG amphiphilic graft copolymers. The composition and the graft architecture of the copolymers were characterized by ¹H NMR, FTIR, and GPC analyses. These amphiphilic graft copolymers could self‐assemble into sphere‐like aggregates in aqueous solution with diverse diameters, which decreased with the increasing of grafting density. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and functionalization of dendron‐polymer conjugate based hydrogels via sequential thiol‐ene “click” reactions

Fabrication and functionalization of hydrogels from well‐defined dendron‐polymer‐dendron conjugates is accomplished using sequential radical thiol‐ene “click” reactions. The dendron‐polymer conjugates were synthesized using an azide‐alkyne “click” reaction of alkene‐containing polyester dendrons bearing an alkyne group at their focal point with linear poly(ethylene glycol)‐bisazides. Thiol‐ene “click” reaction was used for crosslinking these alkene functionalized dendron‐polymer conjugates using a tetrathiol‐based crosslinker to provide clear and transparent hydrogels. Hydrogels with residual alkene groups at crosslinking sites were obtained by tuning the alkene‐thiol stoichiometry. The residual alkene groups allow efficient postfunctionalization of these hydrogel matrices with thiol‐containing molecules via a subsequent radical thiol‐ene reaction. The photochemical nature of radical thiol‐ene reaction was exploited to fabricate micropatterned hydrogels. Tunability of functionalization of these hydrogels, by varying dendron generation and polymer chain length was demonstrated by conjugation of a thiol‐containing fluorescent dye. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 926–934     

Synthesis and characterization of resorcinarene‐centered amphiphilic A8B4 miktoarm star copolymers based on poly(ε‐caprolactone) and poly(ethylene glycol) by combination of CROP and “click” chemistry

Well‐defined amphiphilic A₈B₄ miktoarm star copolymers with eight poly(ethylene glycol) chains and four poly(ε‐caprolactone) arms (R‐8PEG‐4PCL) were prepared using “click” reaction strategy and controlled ring‐opening polymerization (CROP). First, multi‐functional precursor (R‐8N₃‐4OH) with eight azides and four hydroxyls was synthesized based on the derivatization of resorcinarene. Then eight‐PEG‐arm star polymer (R‐8PEG‐4OH) was prepared through “click” reaction of R‐8N₃‐4OH with pre‐synthesized alkyne‐terminated monomethyl PEG (mPEG‐A) in the presence of CuBr/N,N,N′,N″,N″′‐ pentamethyldiethylenetriamine (PMDETA) in DMF. Finally, R‐8PEG‐4OH was used as tetrafunctional macroinitiator to prepare resorcinarene‐centered A₈B₄ miktoarm star copolymers via CROP of ε‐caprolactone utilizing Sn(Oct)₂ as catalyst at 100 °C. These miktoarm star copolymers could self‐assemble into spherical micelles in aqueous solution with resorcinarene moieties on the hydrophobic/hydrophilic interface, and the particle sizes could be controlled by the ratio of PCL to PEG. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2824–2833.     

Macromolecular brushes synthesized by “grafting from” approach based on “click chemistry” and RAFT polymerization

Well‐defined macromolecular brushes with poly(N‐isopropyl acrylamide) (PNIPAM) side chains on random copolymer backbones were synthesized by “grafting from” approach based on click chemistry and reversible addition‐fragmentation chain transfer (RAFT) polymerization. To prepare macromolecular brushes, two linear random copolymers of 2‐(trimethylsilyloxy)ethyl methacrylate (HEMA‐TMS) and methyl methacrylate (MMA) (poly(MMA‐co‐HEMA‐TMS)) were synthesized by atom transfer radical polymerization and were subsequently derivated to azide‐containing polymers. Novel alkyne‐terminated RAFT chain transfer agent (CTA) was grafted to polymer backbones by copper‐catalyzed 1,3‐dipolar cycloaddition (azide‐alkyne click chemistry), and macro‐RAFT CTAs were obtained. PNIPAM side chains were prepared by RAFT polymerization. The macromolecular brushes have well‐defined structures, controlled molecular weights, and molecular weight distributions (M_w/M_n ≦ 1.23). The RAFT polymerization of NIPAM exhibited pseudo‐first‐order kinetics and a linear molecular weight dependence on monomer conversion, and no detectable termination was observed in the polymerization. The macromolecular brushes can self‐assemble into micelles in aqueous solution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 443–453, 2010     

Copper(0)‐catalyzed one‐pot synthesis of ABC triblock copolymers via the combination of single electron transfer nitroxide radical coupling reaction and “click” chemistry

The synthesis of ABC triblock copolymers were accomplished by Cu(0)‐catalyzed one‐pot strategy combining single electron transfer‐nitroxide radical coupling (SET‐NRC) reaction with “click” chemistry. First, the precursors α,ω‐heterofunctionalized poly(ethylene oxide) (PEO) with a 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) group and an alkyne group, polystyrene (PS), and poly(tert‐butyl acrylate) (PtBA) with bromine or azide end group were designed and synthesized, respectively. Then, the one‐pot coupling reactions between these precursors were carried out in the system of Cu(0)/Me₆TREN: The SET‐NRC reaction between bromine group and nitroxide radical group, subsequently click coupling between azide and alkyne group. It was noticeable that Cu(I) generated from Cu(0) by SET mechanism was utilized to catalyze click chemistry. To estimate the effect of Cu(0) on the one‐pot reaction, a comparative analysis was performed in presence of different Cu(0) species. The result showed that Cu(0) with more active surface area could accelerate the one‐pot reaction significantly. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

In situ fabrication of paclitaxel‐loaded core‐crosslinked micelles via thiol‐ene “click” chemistry for reduction‐responsive drug release

In this study, a facile method to fabricate reduction‐responsive core‐crosslinked micelles via in situ thiol‐ene “click” reaction was reported. A series of biodegradable poly(ether‐ester)s with multiple pendent mercapto groups were first synthesized by melt polycondensation of diol poly(ethylene glycol), 1,4‐butanediol, and mercaptosuccinic acid using scandium trifluoromethanesulfonate [Sc(OTf)₃] as the catalyst. Then paclitaxel (PTX)‐loaded core‐crosslinked (CCL) micelles were successfully prepared by in situ crosslinking hydrophobic polyester blocks in aqueous media via thiol‐ene “click” chemistry using 2,2′‐dithiodiethanol diacrylate as the crosslinker. These PTX‐loaded CCL micelles with disulfide bonds exhibited reduction‐responsive behaviors in the presence of dithiothreitol (DTT). The drug release profile of the PTX‐loaded CCL micelles revealed that only a small amount of loaded PTX was released slowly in phosphate buffer solution (PBS) without DTT, while quick release was observed in the presence of 10.0 mM DTT. Cell count kit (CCK‐8) assays revealed that the reduction‐sensitive PTX‐loaded CCL micelles showed high antitumor activity toward HeLa cells, which was significantly higher than that of reduction‐insensitive counterparts and free PTX. This kind of biodegradable and biocompatible CCL micelles could serve as a bioreducible nanocarrier for the controlled antitumor drug release. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 99–107     

Efficient synthesis of well‐defined amphiphilic cylindrical brushes polymer with high grafting density: Interfacial “Click” chemistry approach

Reported here is a novel approach toward efficient preparation of well‐defined cylindrical brushes polymer (CBPs) with both hydrophobic and hydrophilic side chains connected to the linear backbone by interfacial “click” chemistry in two immiscible solvents. The CBPs with high grafting density of more than 95% and molecular polydispersity (M_w/M_n) less than 1.12 can be readily synthesized using present approach. On contrary, the CBPs synthesized from the “click” reaction in a single solvent in homogenous state have low grafting density of less than 55% and molecular polydispersity (M_w/M_n) more than 1.78. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Multiarm star block copolymers via Diels‐Alder click reaction

Two types of multiarm star block copolymers: (polystyrene)_m‐poly(divinylbenzene)‐poly(methyl methacrylate)_n, (PS)_m‐polyDVB‐(PMMA)_n and (polystyrene)_m‐poly(divinylbenzene)‐poly(tert‐butyl acrylate)_k, (PS)_m‐polyDVB‐(PtBA)_k were successfully prepared via a combination of cross‐linking and Diels–Alder click reactions based on “arm‐first” methodology. For this purpose, multiarm star polymer with anthracene functionality as reactive periphery groups was prepared by a cross‐linking reaction of divinyl benzene using α‐anthracene end functionalized polystyrene (PS‐Anth) as a macroinitiator. Thus, obtained multiarm star polymer was then reacted with furan protected maleimide‐end functionalized polymers: PMMA‐MI or PtBA‐MI at reflux temperature of toluene for 48 h resulting in the corresponding multiarm star block copolymers via Diels–Alder click reaction. The multiarm star and multiarm star block copolymers were characterized by using ¹H NMR, SEC, Viscotek triple detection SEC (TD‐SEC) and UV. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 178–187, 2009     

Synthesis of a novel graft copolymer with hyperbranched poly(glycerol) as core and “Y”‐shaped polystyrene‐b‐poly(ethylene oxide)2 as side chains

The graft copolymers composed of “Y”‐shaped polystyrene‐b‐poly(ethylene oxide)₂ (PS‐b‐PEO₂) as side chains and hyperbranched poly(glycerol) (HPG) as core were synthesized by a combination of “click” chemistry and atom transfer radical polymerization (ATRP) via “graft from” and “graft onto” strategies. Firstly, macroinitiators HPG‐Br were obtained by esterification of hydroxyl groups on HPG with bromoisobutyryl bromide, and then by “graft from” strategy, graft copolymers HPG‐g‐(PS‐Br) were synthesized by ATRP of St and further HPG‐g‐(PS‐N₃) were prepared by azidation with NaN₃. Then, the precursors (Bz‐PEO)₂‐alkyne with a single alkyne group at the junction point and an inert benzyl group at each end was synthesized by sequentially ring‐opening polymerization (ROP) of EO using 3‐[(1‐ethoxyethyl)‐ethoxyethyl]‐1,2‐propanediol (EEPD) and diphenylmethylpotassium (DPMK) as coinitiator, termination of living polymeric species by benzyl bromide, recovery of protected hydroxyl groups by HCl and modification by propargyl bromide. Finally, the “click” chemistry was conducted between HPG‐g‐(PS‐N₃) and (Bz‐PEO)₂‐alkyne in the presence of N,N,N′,N″,N”‐pentamethyl diethylenetriamine (PMDETA)/CuBr system by “graft onto” strategy, and the graft copolymers were characterized by SEC, ¹H NMR and FTIR in details. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Preparation of 3‐arm star polymers (A3) via Diels–Alder click reaction

Diels–Alder click reaction was successfully applied for the preparation of 3‐arm star polymers (A₃) using furan protected maleimide end‐functionalized polymers and trianthracene functional linking agent (2) at reflux temperature of toluene for 48 h. Well‐defined furan protected maleimide end‐functionalized polymers, poly (ethylene glycol), poly(methyl methacrylate), and poly(tert‐butyl acrylate) were obtained by esterification or atom transfer radical polymerization. Obtained star polymers were characterized via NMR and GPC (refractive index and triple detector detection). Splitting of GPC traces of the resulting polymer mixture notably displayed that Diels–Alder click reaction was a versatile and a reliable route for the preparation of A₃ star polymer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 302–313, 2008     

Modular synthesis of ABC type block copolymers by “click” chemistry

Heterotelechelic polystyrene (PS), poly(tert‐butyl acrylate) (PtBA), and poly (methyl acrylate) (PMA), containing both azide and triisopropylsilyl (TIPS) protected acetylene end groups, were prepared in good control (M_w/M_n ≤ 1.24) by atom transfer radical polymerization (ATRP). The end groups were independently applied in two successive “click” reactions, that is: first the azide termini were functionalized and, after deprotection, the acetylene moieties were utilized for a second conjugation step. As a proof of concept, PS was consecutively functionalized with propargyl alcohol and azidoacetic acid, as confirmed by MALDI‐ToF MS. In addition, the same methodology was employed to modularly build up an ABC type triblock terpolymer. Size exclusion chromatography measurements demonstrated first coupling of PtBA to PS and, after the deprotection of the acetylene functionality on PS, connection of PMA, yielding a PMA‐b‐PS‐b‐PtBA triblock terpolymer. The reactions were driven to completion using a slight excess of azide functionalized polymers. Reduction of the residual azide groups into amines allowed easy removal of this excess of polymer by column chromatography. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2913–2924, 2007     

Synthesis of amphiphilic biodegradable glycocopolymers based on poly(ε‐caprolactone) by ring‐opening polymerization and click chemistry

Amphiphilic, biodegradable block glycopolymers based on poly(ε‐caprolactone) (PCL) with various pendent saccharides were synthesized by combination of ring‐opening polymerization (ROP) and “click” chemistry. PCL macroinitiators obtained by ROP of ε‐caprolactone were used to initiate the ROP of 2‐bromo‐ε‐caprolactone (BrCL) to get diblock copolymers, PCL‐b‐PBrCL. Reaction of the block copolymers with sodium azide converted the bromine groups in the PBrCL block to azide groups. In the final step, click chemistry of alkynyl saccharides with the pendent azide groups of PCL‐b‐PBrCL led to the formation of the amphiphilic block glycopolymers. These copolymers were characterized by ¹H NMR spectroscopy and gel permeation chromatography. The self‐assembly behavior of the amphiphilic block copolymers was investigated using transmission electron microscopy and atomic force microscope, spherical aggregates with saccharide groups on the surface were observed, and the aggregates could bind reversibly with Concanavalin A. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3583–3594, 2009     

Synthesis of biocompatible and biodegradable block copolymers of polyvinyl alcohol‐block‐poly(ε‐caprolactone) using metal‐free living cationic polymerization

Applications of metal‐free living cationic polymerization of vinyl ethers using HCl · Et₂O are reported. Product of poly(vinyl ether)s possessing functional end groups such as hydroxyethyl groups with predicted molecular weights was used as a macroinitiator in activated monomer cationic polymerization of ε‐caprolactone (CL) with HCl · Et₂O as a ring‐opening polymerization. This combination method is a metal‐free polymerization using HCl · Et₂O. The formation of poly(isobutyl vinyl ether)‐b‐poly(ε‐caprolactone) (PIBVE‐b‐PCL) and poly(tert‐butyl vinyl ether)‐b‐poly(ε‐caprolactone) (PTBVE‐b‐PCL) from two vinyl ethers and CL was successful. Therefore, we synthesized novel amphiphilic, biocompatible, and biodegradable block copolymers comprised polyvinyl alcohol and PCL, namely PVA‐b‐PCL by transformation of acid hydrolysis of tert‐butoxy moiety of PTBVE in PTBVE‐b‐PCL. The synthesized copolymers showed well‐defined structure and narrow molecular weight distribution. The structure of resulting block copolymers was confirmed by ¹H NMR, size exclusion chromatography, and differential scanning calorimetry. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5169–5179, 2009     

Preparation of polyHIPE via CuAAC “click” chemistry and its application as a highly efficient adsorbent of Cu(II) ions

A hydrophilic emulsion‐templated porous polymer (polyHIPE) is synthesized by CuAAC “click” chemistry. Herein, a 4,4′‐diazidostilbene‐2,2′‐disulfonic acid disodium salt‐4H₂O (DAS) and tripropargylamine in the mixture of water and N,N‐dimethylformamide solution is used as external phase of the high internal phase emulsion template, and paraffin liquid is involved as the internal phase. The resulting polyHIPE has a well‐defined interconnected pore structure, which could be tailored by changing preparation parameters, such as reagent content, internal phase volume fraction, and surfactant concentration. Thermal analysis shows that the polyHIPE is stable under 180 °C. Owing to the presence of a large number of sodium sulfonate groups from the reagent DAS and the triazoles groups produced in the reaction, the polyHIPE is proved to be a highly efficient adsorbent of heavy metal ion (i.e., up to 52 mg/g for Cu(II) ions) in water. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2129–2135     

Block copolymers of poly(ethylene oxide) and poly(vinyl alcohol) synthesized by the RAFT methodology

A methodology for the synthesis of well‐defined poly(ethylene oxide)‐block‐poly(vinyl alcohol) (PEO‐b‐PVA) and PVA‐b‐PEO‐b‐PVA polymers was reported. Novel xanthate end‐functionalized PEOs were synthesized by a series of end‐group transformations. They were then used to mediate the reversible addition–fragmentation chain transfer polymerization of vinyl acetate to obtain well‐defined poly(ethylene oxide)‐b‐poly(vinyl acetate) (PEO‐b‐PVAc) and PVAc‐b‐PEO‐b‐PVAc. When these block copolymers were directly hydrolyzed in methanol solution of sodium hydroxide, polymers with brown color were obtained, which was due to the formation of conjugated unsaturated aldehyde structures. To circumvent these side reactions, the xanthate groups were removed by adding a primary amine before hydrolysis and the products thus obtained were white powders. The polymers were characterized by gel permeation chromatography, ¹H NMR spectroscopy and FT‐IR. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1901–1910, 2009     

Three‐arm star ring opening metathesis polymers via alkyne‐azide click reaction

The click chemistry strategy is successfully applied for the preparation of three‐arm star (A₃) ring opening metathesis polymers. A well‐defined monoazide end‐functionalized poly(N‐ethyl oxanorbornene) and a poly(N‐butyl oxanorbornene) obtained via ring opening metathesis polymerization using first generation Grubbs' catalyst are simply clicked with the trisalkyne core affording the synthesis of target star polymers. The obtained star polymers are characterized via nuclear magnetic resonance spectroscopy and gel permeation chromatography (GPC). The deconvolution analyses of GPC traces reveal that the click reaction efficiency for the star formation strongly depends on the chemical nature and the molecular weight of ROM polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2344–2351, 2009     

Synthesis of Novel Core Cross‐Linked Star‐Based Polyrotaxane End‐Capped via “CuAAC” Click Chemistry

The first example of core cross‐linked star (CCS) polyrotaxane was prepared using the poly(ϵ‐caprolactone) (PCL) CCS three‐dimensional (3D) scaffold. The 3D CCS polymer was firstly prepared through the “arm‐first” approach. Then, the “arms” of the resultant PCL CCS polymer were threaded with α‐cyclodextrins (α‐CDs). The threaded α‐CDs were permanently locked by the “click” reaction of terminal alkyne functionalities of the star polymers with the azide‐functionalized end caps to afford the CCS polyrotaxanes. All analytical results confirm the formation of the CCS polyrotaxanes and reveal their characteristics, including fluorescence under UV, a channel‐type crystalline structure, a two‐step thermal decomposition, and a unique core‐shell structure in great contrast to the polymer precursors.     

In situ polymerization and morphology of polypyrrole obtained in water‐soluble polymer templates

Several water‐soluble polymers were used as templates for the in situ polymerization of pyrrole to determine their effect on the generation of nanosized polypyrrole (PPy) particles. The polymers used include: polyvinyl alcohol (PVA), polyethylene oxide (PEO), poly(vinyl butyral), polystyrene sulfonic acid, poly(ethylene‐alt‐maleic anhydride) (PEMA), poly(octadecene‐alt‐maleic anhydride), poly(N‐vinyl pyrrolidone), poly(vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate), poly(N‐isopropyl acrylamide), poly(ethylene oxide‐block‐propylene oxide), hydroxypropyl methyl cellulose, and guar gum. The oxidative polymerization of pyrrole was carried out with FeCl₃ as an oxidant. The morphology of PPy particles obtained after drying the resulting aqueous dispersions was examined by optical microscopy, and selected samples were further analyzed via atomic force microscopy. Among the template polymers, PVA was the most efficient in generating stable dispersions of PPy nanospheres in water, followed by PEO and PEMA. The average size of PPy nanospheres was in the range of 160 nm and found to depend on the molecular weight and concentration of PVA. Model reactions and kinetics of the polymerization reaction of pyrrole in PVA were carried out by hydrogen ¹H NMR spectroscopy using ammonium persulfate as an oxidant. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012