Poly(p‐phenylene methylene)‐based block copolymers by mechanistic transformation

The synthesis of poly(p‐phenylene methylene) (PPM)‐based block copolymers such as poly(p‐phenylene methylene)‐b‐poly(ε‐caprolactone) and poly(p‐phenylene methylene)‐b‐polytetrahydrofuran by mechanistic transformation was described. First, precursor PPM was synthesized by acid‐catalyzed polymerization of tribenzylborate at 16 °C. Then, this polymer was used as macroinitiators in either ring‐opening polymerization of ε‐caprolactone or cationic ring‐opening polymerization of tetrahydrofuran to yield respective block copolymers. The structures of the prepolymer and block copolymers were characterized by GPC and ¹H NMR investigations. The composition of block copolymers as determined by ¹H NMR and TGA analysis was found to be in very good agreement. The thermal behavior and surface morphology of the copolymers were also investigated, respectively, by differential scanning calorimetry and atomic force microscopy measurements, and the contribution of the major soft segment has been observed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and Characterization of Amphiphilic Poly(caprolactone) Star Block Copolymers

Summary: Novel, star‐shaped, amphiphilic block copolymers composed of fully degradable poly(caprolactone) were synthesized by sequential addition polymerization. In the first step, four‐arm macroinitiators were produced by ring‐opening polymerization of caprolactone by initiation with pentaerythritol. Then, block copolymers were synthesized by sequential addition of 4‐(2‐benzyloxyethyl)‐ε‐caprolactone to the four‐arm macroinitiators. Star‐shaped, amphiphilic block copolymers containing poly(caprolactone)‐block‐poly[4‐(2‐hydroxyethyl)caprolactone] segments were obtained by catalytic debenzylation.

Four‐arm amphiphilic polycaprolactone star block copolymer.     

Soluble tin(II) macroinitiator adducts for the controlled ring‐opening polymerization of lactones and cyclic carbonates

Polyesters and poly(ester carbonates) were synthesized via ring‐opening polymerization with new tin(II) macroinitiator adducts containing oligomeric L ‐lactide (LLA), rac‐lactide (rac‐LA), and ?‐caprolactone (CL). The novel initiating species were synthesized by the reaction of LLA, rac‐LA, or CL with Sn(OEt)₂ (monomer concentration/initiator concentration ≤20) and then were dissolved in methylene chloride or toluene and stored in a stoppered flask for the subsequent ring‐opening polymerization of cyclic esters and carbonates. The soluble tin alkoxide macroinitiators yielded predictable and quantitative initiation of polymerization for up to 1 month of storage time at room temperature. The resulting polymers displayed low polydispersity (≤1.5), and a high monomer conversion (>95%) was obtained within relatively short polymerization times (≤2 h). Adjusting the monomer/macroinitiator ratio effectively controlled the molecular weights of the polymers. NMR was used to characterize the initiating species and polymer microstructure, and size exclusion chromatography was used to determine the molecular weight properties of the polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3434–3442, 2002     

Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO2‐Based Block Copolymers from Monomer Mixtures

Switchable polymerization provides the opportunity to regulate polymer sequence and structure in a one‐pot process from mixtures of monomers. Herein we report the use of O₂ as an external stimulus to switch the polymerization mechanism from the radical polymerization of vinyl monomers mediated by (Salen)Co^III?R [Salen=N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediamine; R=alkyl] to the ring‐opening copolymerization (ROCOP) of CO₂/epoxides. Critical to this process is unprecedented monooxygen insertion into the Co?C bond, as rationalized by DFT calculations, leading to the formation of (Salen)Co^III?O?R as an active species to initiate ROCOP. Diblock poly(vinyl acetate)‐b‐polycarbonate could be obtained by ROCOP of CO₂/epoxides with preactivation of (Salen)Co end‐capped poly(vinyl acetate). Furthermore, a poly(vinyl acetate)‐b‐poly(methyl acrylate)‐b‐polycarbonate triblock copolymer was successfully synthesized by a (Salen)cobalt‐mediated sequential polymerization with an O₂‐triggered switch in a one‐pot process.     

Synthesis and characterization of two classes of hyperstar polymers bearing hyperbranched cores grafted with linear arms

New hyperstar polymers (HSP) consisting of two different hyperbranched (hb) aromatic/aliphatic cores grafted with linear polymer arms were successfully synthesized. The hb cores were based on either hb poly(vinylbenzylchloride) synthesized by SCVP‐ATRP or hb polyester from a polycondensation reaction. For the core‐first approach, the hb cores have been modified to hb macroinitiators initiating either the cationic ring‐opening polymerization of oxazolines (Oxa) or the atom transfer radical polymerization of alkylmethacrylates. For potential use as reactive binders in epoxy coatings the HSPs were equipped with a defined amount of OH‐groups during arm growth via controlled block‐copolymerization with nonfunctionalized and OH‐functionalized monomers, either an oxazoline (OH)Oxa (2‐[1‐(hydroxymethyl)ethyl]‐oxazoline) or a methacrylate HEMA (2‐hydroxyethyl methacrylate). The amount of OH‐groups could be well adjusted in this way. The hyperstars were comprehensively characterized with respect to chemical structure and molecule dimension. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 000: 000–000, 2012     

New aliphatic poly(ester‐carbonates) based on 5‐methyl‐5‐allyloxycarbonyl‐1,3‐dioxan‐2‐one

The synthesis, characterization, and ring‐opening polymerization of a new cyclic carbonate monomer containing an allyl ester moiety, 5‐methyl‐5‐allyloxycarbonyl‐1,3‐dioxan‐2‐one (MAC), was performed for the first time. MAC was synthesized in five steps in good yield beginning from the starting material, 2,2‐bis(hydroxymethyl)propionic acid. Subsequent polymerization and copolymerizations of the new cyclic carbonate with rac‐lactide (rac‐LA) and ?‐caprolactone (CL) were attempted. Rac‐LA copolymerized well with MAC, but CL copolymerizations produced insoluble products. Oligomeric macroinitiators of MAC and rac‐LA were synthesized from stannous ethoxide, and both macroinitiators were used for the controlled ring‐opening polymerization of rac‐LA. The polymerization kinetics were examined by monitoring the disappearance of the characteristic C? O ring stretch of the monomer at 1240 cm^?1 with real‐time in situ Fourier transform infrared spectroscopy. Postpolymerization oxidation reactions were conducted to epoxidize the unsaturated bonds of the MAC‐functionalized polymers. Epoxide‐containing polymers may allow further organic transformations with various nucleophiles, such as amines, alcohols, and carboxylic acids. NMR was used for microstructure identification of the polymers, and size exclusion chromatography and differential scanning calorimetry were used to characterize the new functionalized poly(ester‐carbonates). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1978–1991, 2003     

Synthesis and cationic ring‐opening polymerization of oxetane monomer containing five‐membered cyclic carbonate moiety via highly chemoselective addition of CO2

The bicyclic amidinium iodide effectively catalyzed the reaction of carbon dioxide and the epoxy‐containing oxetane under ordinary pressure and mild conditions with high chemoselectivity to give the corresponding oxetane monomer containing five‐membered cyclic carbonate quantitatively. The cationic ring‐opening polymerization of the obtained monomer by boron trifluoride diethyl ether proceeded to give linear polyoxetane bearing five‐membered cyclic carbonate pendant group in high yield. The molecular weight of the polyoxetane was higher than that of polyepoxide obtained by the cationic ring‐opening polymerization of epoxide monomer containing five‐membered cyclic carbonate. The cyclic carbonate functional crosslinked polyoxetanes were also synthesized by the cationic ring‐opening copolymerization of cyclic carbonate having oxetane and commercially available bisoxetane monomers. Analyses of the resulting polyoxetanes were performed by proton nuclear magnetic resonance, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2606–2615     

Homopolymerization and copolymerization kinetics of trimethylene carbonate bearing a methoxyethoxy side group

The polymerization kinetics of 5‐[2‐{2‐(2‐methoxyethoxy)ethyoxy}‐ethoxymethyl]‐5‐methyl‐trimethylene carbonate (TMCM‐MOE3OM) synthesized using the organocatalyst 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) were studied and compared to those with the commonly used catalyst/initiator for ring‐opening polymerization of cyclic carbonates and esters, stannous 2‐ethylhexanoate. Further, the utility of each of these catalysts in the copolymerization of TMCM‐MOE3OM with trimethylene carbonate (TMC) and l ‐lactide (LLA) was examined. Regardless of conditions with either catalyst, homopolymerization of TMCM‐MOE3OM yielded oligomers, having number average molecular weight less than 4000 Da. The resultant molecular weight was limited by ring‐chain equilibrium as well as through monomer autopolymerization. Interestingly, autopolymerization of TMC was also achieved with DBU as the catalyst. Copolymerization with TMC using stannous 2‐ethylhexanoate as the catalyst yielded random copolymers, while diblock copolymers were formed by copolymerization with LLA. With DBU as the catalyst, copolymers with LLA could not be formed, while blocky copolymers were formed with TMC. These findings should be useful in the incorporation of this monomer in the design of polymer biomaterials. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 544–552     

Functionalized PEG‐b‐PAGE‐b‐PLGA triblock terpolymers as materials for nanoparticle preparation

A series of poly(ethylene glycol)‐block‐poly(allyl glycidyl ether) (PEG‐b‐PAGE) macroinitiators are prepared using the living anionic ring‐opening polymerization (AROP) technique, and applied for further copolymerization studies. To overcome the low reactivity of the secondary hydroxyl end‐group of the PAGE block, a primary hydroxyl group is introduced into the macroinitiators via trityl and tert‐butyl‐dimethylsilane protective groups. The modified macroinitiators are used for copolymerization by applying different amounts of PEG‐b‐PAGE (5, 10, and 15%) and different PLGA lengths. To study their properties, nanoparticles from selected polymers are prepared and characterized by dynamic light scattering and scanning electron microscopy showing spherical particles with diameters around 200 nm and low PDI_particle values of 0.03–0.1. An advantage of the obtained polymers is the presence of double bonds in the side chain, which enables the modification via, for example, thiol‐ene reactions. For this purpose tertiary 2‐(dimethylamino)ethanethiol), acetylated thiogalactose and thiomannose are attached onto the double bonds of the PAGE‐blocks. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2163–2174     

Amphiphilic star‐block copolymers based on a hyperbranched core: Synthesis and supramolecular self‐assembly

Novel amphiphilic star‐block copolymers, star poly(caprolactone)‐block‐poly[(2‐dimethylamino)ethyl methacrylate] and poly(caprolactone)‐block‐poly(methacrylic acid), with hyperbranched poly(2‐hydroxyethyl methacrylate) (PHEMA–OH) as a core moiety were synthesized and characterized. The star‐block copolymers were prepared by a combination of ring‐opening polymerization and atom transfer radical polymerization (ATRP). First, hyperbranched PHEMA–OH with 18 hydroxyl end groups on average was used as an initiator for the ring‐opening polymerization of ε‐caprolactone to produce PHEMA–PCL star homopolymers [PHEMA = poly(2‐hydroxyethyl methacrylate); PCL = poly(caprolactone)]. Next, the hydroxyl end groups of PHEMA–PCL were converted to 2‐bromoesters, and this gave rise to macroinitiator PHEMA–PCL–Br for ATRP. Then, 2‐dimethylaminoethyl methacrylate or tert‐butyl methacrylate was polymerized from the macroinitiators, and this afforded the star‐block copolymers PHEMA–PCL–PDMA [PDMA = poly(2‐dimethylaminoethyl methacrylate)] and PHEMA–PCL–PtBMA [PtBMA = poly(tert‐butyl methacrylate)]. Characterization by gel permeation chromatography and nuclear magnetic resonance confirmed the expected molecular structure. The hydrolysis of tert‐butyl ester groups of the poly(tert‐butyl methacrylate) blocks gave the star‐block copolymer PHEMA–PCL–PMAA [PMAA = poly(methacrylic acid)]. These amphiphilic star‐block copolymers could self‐assemble into spherical micelles, as characterized by dynamic light scattering and transmission electron microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6534–6544, 2005     

Polymerization of cyclic imino ethers: From its discovery to the present state of the art

Topics concerning the cationic ring‐opening polymerization of cyclic imino ethers and functional material production based on the resulting polymers are reviewed. Cyclic imino ethers are readily subjected to isomerization polymerization via cationic initiators. Mechanistic studies have provided a new concept, electrophilic polymerization. Double isomerization polymerization and no‐catalyst alternating copolymerization are interesting examples that show characteristics of the ring opening of cyclic imino ethers. The living polymerization of these monomers affords precisely controlled polymeric materials. Through the use of the unique properties of the product polymers, various functional polymeric materials, such as polymeric nonionic surfactants, compatibilizers, hydrogels, stabilizers for dispersion polymerization, biocatalyst modifiers, and supramolecular assemblies, have been developed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 192–209, 2002     

Novel multifunctional polymeric materials with predominant cis microstructures derived from α‐norbornenyl macromonomer and stable macroinitiator via ring‐opening metathesis polymerization and atom transfer radical polymerization

Novel star‐like polymeric materials with high cis content could be obtained by using α‐norbornenyl macromonomers and highly stable macroinitiators derived from an active norbornene derivative [5‐(2‐bromo‐2‐methylpropionylaminomethyl)bicyclo[2.2.1]hept‐2‐ene (NBBrMPAM)], which was synthesized by the reaction of norbornene methylene amine and 2‐bromo‐2‐methylpropionyl bromide. The α‐norbornenyl macromonomer (NBPMMA), which is polymethyl methacrylate containing norbornenyl end group, was prepared by atom transfer radical polymerization (ATRP) using NBBrMPAM as an initiator. Star‐like polynorbornene with high cis microstructure (cis/trans = 72/28) was obtained directly by ring‐opening metathesis polymerization of NBPMMA macromonomer having number molecular weight (Mn ) as low as 6.39 × 10³. Random ring‐opening metathesis copolymerization of NBPMMA and norbornene derivative containing carbazole group (NBCbz) was carried out at 25 °C by using Ru catalyst [(Cy₃P)₂Cl₂Ru = CHPh, Cy = cyclohexyl, Ph = phenyl]. High cis (cis/trans = 63/37) organo‐soluble star‐like random poly(NBPMMA‐co‐NBCbz) was successfully obtained with high number‐average molecular weight (Mn ) of 4.76 × 10⁴ and molecular weight distribution polydispersity index of 1.78. Organo‐soluble comb‐shaped copolymers with MMA could be successfully obtained using ATRP macroinitiator [poly(HNBBrMPAM)] in diluted macroinitiator solution with a concentration less than 3.64 × 10^?2 mol.L^?1. This is the first ever attempt to prepare novel star‐like organo‐soluble polymeric materials with high cis microstructure via the combination of ring‐opening metathesis polymerization and ATRP. Multimodification could be considered to be carried out by using the functional bromo group at the end of side chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3382–3392, 2006     

Preparation of the amphiphilic macro‐rings of poly(ethylene oxide) with multi‐polystyrene lateral chains and their extraction for dyes

A novel method for synthesis of amphiphilic macrocyclic graft copolymers with multi‐polystyrene lateral chains is suggested, by combination of anionic ring‐open polymerization (AROP) with atom transfer radical polymerization (ATRP). The anionic ring‐opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using triethylene glycol and diphenylmethylpotassium (DPMK) as coinitiators; the monomer reactivity ratio of them are r_1(EO) = 1.20 ± 0.01 and r_2(EEGE) = 0.76 ± 0.02 respectively. The obtained linear well‐defined α,ω‐dihydroxyl poly(ethylene oxide) with pendant protected hydroxylmethyls (l‐poly(EO‐co‐EEGE)) was cyclized by reaction with tosyl chloride (TsCl) in the presence of solid KOH. The crude cyclized product containing the extended linear chain polymer was hydrolyzed and then purified by treat with α‐CD. The pure cyclic copolymer with multipendant hydroxymethyls [c‐poly(EO‐co‐Gly)] was esterified by reaction with 2‐bromoisobutyryl bromide, and then used as macroinitiators to initiate polymerization of styrene (St), and a series of amphiphilic macrocyclic grafted copolymers composed of a hydrophilic PEO as ring and hydrophobic polystyrene as side chains (c‐PEO‐g‐PS) were obtained. The intermediates and final products were characterized by GPC, NMR and MALDI‐TOF in detail. The experimental results confirmed that c‐PEO‐g‐PS shows stronger conjugation ability with the dyes than the corresponding comb‐PEO‐g‐PS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5824–5837, 2007     

Polymerization of epoxidized vegetable oil derivatives: Ionic‐coordinative polymerization of methylepoxyoleate

Ring‐opening polymerization of epoxidized methyloleate (EMO) with various ionic‐coordinative initiators have been studied and compared with other internal epoxy monomers: benzyl 9,10‐epoxyoleoylether and cis‐4,5‐epoxyoctane. The structure and molecular weight of the resulting polymers have been studied by ¹H‐ and ¹³C‐NMR, MALDI‐TOF‐MS, and size exclusion chromatography analysis. Polymers with higher molecular weight than those obtained with conventional cationic catalyst are obtained. These materials have been found to consist of a complex mixture of cyclic and linear polymer chains with different chain ends that can be related to the catalyst nature and the occurrence of two main polymerization mechanisms, the cationic and the ionic‐coordinative. In the polymerization of EMO, transesterification by‐side reactions leading to ester linkages in the main chain have been identified. These undesired reactions have been suppressed by copolymerization with small amounts of tetrahydrofuran with no substantial decrease in the polymer yield and molecular weight. Finally, the polymerization of EMO has been tested in a larger scale to prepare a renewable resource‐based polyether as starting material to produce polyether polyols for polyurethane applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Recent Advances in Free-Radical Ring-Opening Polymerization

Although cyclic ketene acetals, such as 2-methylene-1, 3-dioxepane, undergo quantitative free-radical ring-opening polymerization, their reactivity in copolymerization is rather low. In order to find a series of monomers that have high reactivities in copolymerization and still undergo free radical ring-opening polymerization, a series of cyclic acrylates was synthesized and polymerized. For example, β-bromolactic acid condensed with benzaldehyde to give a cyclic acetal lactone which on treatment with base gave the cyclic acrylate. Free-radical solution polymerization at 140°C of the cyclic acrylate, which produced a benzyl radical upon ring opening, gave quantitative ring opening. However, in bulk at 120°C, only 20% of the rings were opened during poiymerization. The resulting polymers containing the pyruvate ester units were shown to be highly biodegradable with microorganisms. Vesicles containing these cyclic acrylates on the end of one of the hydrophobic chains of the lipidlike molecules were shown to undergo free-radical ring-opening polymerization to give polymerized vesicles which were biodegradable. In order to discover groups other than carbonyl groups and strained rings that would promote free-radical ring-opening polymerization, a series of spiromethylenecyclohexadienes were prepared and polymerized. Thus, 3-methylenespiro [5,5] undeca-1,4-diene in bulk at 130°C gave a polymer in which 79% of the rings had opened and in solution at 130°C gave a polymer in which nearly all of the rings had opened. A benzo derivative, 3-methylene-8,9-benzo [5,5] undeca-1,4,8-triene, gave a polymer that is essentially an alternating copolymer of p-xylylene and o-xylylene and has a very high thermal decomposition temperature. A tricyclic dispirocyclohexadiene derivative was shown to undergo double free-radical ring-opening polymerization to give a polymer with expansion in volume containing a p-phenylene group in the backbone.     

Hydroxyfunctional oxetane‐inimers with varied polarity for the synthesis of hyperbranched polyether polyols via cationic ROP

Synthesis and characterization of novel hydroxyl‐functionalized oxetane‐inimers with varied alkyl chain length—3‐hydroxymethyl‐3‐methoxymethyloxetane, 3‐hydroxymethyl‐3‐propoxymethyloxetane, and 3‐hexoxymethyl‐3‐hydroxymethyloxetane—is reported. Cationic ring‐opening polymerization of these latent, cyclic AB₂‐monomers leads to hyperbranched (hb) polyether polyols with degrees of branching between 34 and 69%, confirmed by inverse‐gated (IG) ¹³C NMR spectroscopy. The hyperbranching polymerization yielded apparent molecular weights (M_n) ranging from 500 to 2500 g mol^?1 (size exclusion chromatography). Remarkably, by copolymerization of 1,1,1‐tris(4‐hydroxyphenyl)ethane as a “focal” unit, polymerization under slow monomer addition conditions lead to higher apparent molecular weights up to 11,220 g mol^?1. The end groups of the hb polymers were studied via matrix‐assisted laser desorption/ionization time of flight mass and NMR spectrometry. By varying the alkyl chain length, tailoring of the solubility and glass transition temperatures of the materials is possible. Potential applications range from macroinitiators with defined polarity to tailoring of surface properties of antifouling materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2850–2859     

Homopolymerization and Copolymerization of Adipic Anhydride with ε-Caprolactone Catalyzed by Rare Earth Trisphenolate

The ring-opening polymerization of adipic anhydride and the ring-opening copolymerization of adipic anhydride with ε-caprolactone catalyzed by single component rare earth trisphenolate have been reported. The structure of the copolymer poly（CL-b-AA） has been characterized by SEC, ^1H NMR and DSC.     

Synthesis and characterization of highly fluorescent polythiophene derivatives containing polystyrene sidearms

In this study, macroinitiators with different content of atom‐transfer radical polymerization (ATRP) functional group on polythiophene backbone were first prepared by the copolymerization of 3‐[1‐ethyl‐2‐(2‐bromopropionate)]thiophene and 3‐hexylthiophene with various feed ratio. Then poly [3‐hexyl‐2,5‐thienylene‐co‐3‐[1‐ ethyl‐2‐(2‐[poly(styrene)]propionate)]‐2,5‐thienylene] (PTTBr‐PS) with different graft density were obtained by ATRP of styrene from these macroinitiators in anisole. The degree of polymerization of PS sidearm (DP_PS) was controlled by polymerization time. The structures of obtained graft copolymers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (¹H NMR) and differential scanning calorimetry (DSC). Introduction of the PS sidearms onto the backbone of polythiophene was an attempt to trap the polythiophene backbone in a “solution‐like” conformation, thus inhibit the packing of polythiophene backbone and result in the improvement of fluorescent property in solid state. This was verified by the UV–vis and fluorescence analyses. Besides, it was also found that the optical property of PTTBr‐PS graft copolymer was dominated by its graft density and independent on the degree of polymerization of its PS sidearm. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1003–1013, 2008     

Poly(ϵ‐caprolactone‐b‐glycolide) and poly(D,L‐lactide‐b‐glycolide) diblock copolyesters: Controlled synthesis,characterization, and colloidal dispersions

Living ω‐aluminum alkoxide poly‐ϵ‐caprolactone and poly‐D,L ‐lactide chains were synthesized by the ring‐opening polymerization of ϵ‐caprolactone (ϵ‐CL) and D,L ‐lactide (D,L ‐LA), respectively, and were used as macroinitiators for glycolide (GA) polymerization in tetrahydrofuran at 40 °C. The P(CL‐b‐GA) and P(LA‐b‐GA) diblock copolymers that formed were fractionated by the use of a selective solvent for each block and were characterized by ¹H NMR spectroscopy and differential scanning calorimetry analysis. The livingness of the operative coordination–insertion mechanism is responsible for the control of the copolyester composition, the length of the blocks, and, ultimately, the thermal behavior. Because of the inherent insolubility of the polyglycolide blocks, microphase separation occurs during the course of the sequential polymerization, resulting in a stable, colloidal, nonaqueous copolymer dispersion, as confirmed by photon correlation spectroscopy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 294–306, 2001     

Orthogonal multifunctionalization of aliphatic polycarbonate via sequential Michael addition and radical‐thiol‐ene click reactions

Aliphatic polycarbonate (PC) copolymer is synthesized by ring opening copolymerization of acrylate‐ and allyl‐functional cyclic carbonate monomers. The post‐polymerization functionalization of the resulting copolymer is performed quantitatively using a variety of thiol compounds via sequential Michael addition and photo‐induced radical thiol‐ene click reactions within relatively short reaction time at ambient temperature. This metal‐free click chemistry methodology affords the synthesis of biocompatible PC copolymer with multifunctional groups. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1581–1587