Preparation of macroporous functionalized polymer beads by a multistep polymerization and their application in zirconocene catalysts for ethylene polymerization

Macroporous functionalized polymer beads of poly(4‐vinylpyridine‐co‐1,4‐divinylbenzene) [P(VPy‐co‐DVB)] were prepared by a multistep polymerization, including a polystyrene (PS) shape template by emulsifier‐free emulsion polymerization, linear PS seeds by staged template suspension polymerization, and macroporous functionalized polymer beads of P(VPy‐co‐DVB) by multistep seeded polymerization. The polymer beads, having a cellular texture, were made of many small, spherical particles. The bead size was 10–50 μm, and the pore size was 0.1–1.5 μm. The polymer beads were used as supports for zirconocene catalysts in ethylene polymerization. They were very different from traditional polymer supports. The polymer beads could be exfoliated to yield many spherical particles dispersed in the resulting polyethylene particles during ethylene polymerization. The influence of the polymer beads on the catalytic behavior of the supported catalyst and morphology of the resulting polyethylene was investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 873–880, 2003     

Hairy polymeric nanocapsules with ph‐responsive shell and thermoresponsive brushes: Tunable permeability for controlled release of water‐soluble drugs

The hairy poly(methacrylic acid‐co‐divinylbenzene)‐g‐poly(N‐isopropylacrylamide) (P(MAA‐co‐DVB)‐g‐PNIPAm) nanocapsules with pH‐responsive P(MAA‐co‐DVB) inner shell and temperature‐responsive PNIPAm brushes were prepared by combined distillation–precipitation copolymerization and surface thiol‐ene click grafting reaction using 3‐(trimethoxysilyl)propyl methacrylate‐modified silica (SiO₂‐MPS) nanospheres as a sacrificial core material. The well‐defined PNIPAm was synthesized by a reversible addition fragmentation chain transfer (RAFT) polymerization. The chain end was converted to a thiol by chemical reduction. The PNIPAm was integrated into the nanocapsules via thiol‐ene click reaction. The surface thiol‐ene click reaction conduced to tunable grafting density of PNIPAm brushes. The grafting densities decreased from 0.70 chains nm^?2 to 0.15 chains nm^?2 with increasing the molecular weight of grafted PNIPAm chains. Using water soluble doxorubicin hydrochloride (DOX·HCl) as a model molecular, the tunable shell permeability of the nanocapsule was investigated in detail. The permeability constant can be tuned by controlling the thickness of the P(MAA‐co‐DVB) inner shell, the grafting density of PNIPAm brushes, and the environmental pH and temperature. The tunable shell permeability of these nanocapsules results in the release of the loaded guest molecules with manipulable releasing kinetics. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2202–2216     

Synthesis and characterization of amphiphilic block copolymers with allyl side‐groups

The synthesis of a new cyclic carbonate monomer containing an allyl group was reported and its biodegradable amphiphilic block copolymer, poly(ethylene glycol)‐block‐poly(L ‐lactide‐co‐5‐methyl‐5‐allyloxycarbonyl‐propylene carbonate) [PEG‐b‐P(LA‐co‐MAC)] was synthesized by ring‐opening polymerization (ROP) of L ‐lactide (LA) and 5‐methyl‐5‐allyloxycarbonyl‐1,3‐dioxan‐2‐one (MAC) in the presence of poly (ethylene glycol) as a macroinitiator, with diethyl zinc as a catalyst. ¹³C NMR and ¹H NMR were used for microstructure identification of the copolymers. The copolymer could form micelles in aqueous solution. The core of the micelles is built of the hydrophobic P(LA‐co‐MAC) chains, whereas the shell is set up by the hydrophilic PEG blocks. The micelles exhibited a homogeneous spherical morphology and unimodal size distribution. By using the cyclic carbonate monomer containing allyl side‐groups, crosslinking of the PEG‐b‐P(LA‐co‐MAC) inner core was possible. The adhesion and spreading of ECV‐304 cells on the copolymer were better than that on PLA films. Therefore, this biodegradable amphiphilic block copolymer is expected to be used as a biomaterial for drug delivery and tissue engineering. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5518–5528, 2007     

Clicked (AB)2C‐type miktoarm terpolymers: Synthesis,thermal and self‐assembly properties,and preparation of nanoporous materials

A well‐defined (PEO‐PS)₂‐PLA miktoarm terpolymer ( 1 ) was synthesized by stepwise click reactions of individually prepared poly(ethylene oxide) (PEO), polystyrene (PS, polymerized by atom transfer radical polymerization), and polylactide (PLA, polymerized by ring‐opening polymerization) blocks. As characterized by differential scanning calorimetry and small‐angle X‐ray scattering techniques, the terpolymer self‐assembled into a hexagonal columnar structure consisting of PLA/PEO cylindrical cores surrounded by PS chains. In contrast, the ion‐doped sample ( 1‐Li⁺ ) with lithium concentration per ethylene oxide = 0.2 exhibited a three‐phase lamellar structure, which was attributed to the microphase separation between PEO and PLA blocks and to the conformational stabilization of the longest PLA chain. The two‐phase columnar morphology before the ion doping was used to prepare a nanoporous material. PLA chains in the cylindrical core region were hydrolyzed by sodium hydroxide, producing nanopores with a pore diameter of about 14 nm. The resulted nanoporous material sank to the bottom in water, because of water‐compatible PEO chains on the walls. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Methylated and pegylated PLA–PCL–PLA block copolymers via the chemical modification of di‐hydroxy PCL combined with the ring opening polymerization of lactide

Methylated and pegylated poly(lactide)‐block‐poly(ε‐caprolactone)‐block‐poly(lactide) copolymers, PLA–P(CL‐co‐CLCH₃)–PLA and PLA–P(CL‐co‐CLPEG)–PLA, were prepared in three steps: combining the formation of carbanion‐bearing dihydroxylated‐PCL, the coupling of iodomethane or bromoacetylated α‐hydroxyl‐ω‐methoxy‐poly(ethylene glycol) onto the carbanionic PCL, and finally the ring opening polymerization of DL ‐lactide initiated by the preformed grafted diOH‐PCL copolymers. The resulting block copolymers exhibited lower crystallinity, melting temperature, and hydrophobicity with respect to the original PCL. Degradation of the grafted copolymers was investigated in the presence of Pseudomonas cepacia lipase and compared with that of the triblock copolymer precursor. It is shown that the presence of the grafted substituents affected the enzymatic degradation of PCL segments. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4196–4205, 2005     

Elaboration of densely functionalized polylactide nanoparticles from N‐acryloxysuccinimide‐based block copolymers

Poly(N‐acryloxysuccinimide) (PNAS) and poly(N‐acryloxysuccinimide‐co‐N‐vinylpyrrolidone) (P(NAS‐co‐NVP)) of adjustable molecular weights and narrow polydispersities were prepared by nitroxide‐mediated polymerization (NMP) in N,N‐dimethylformamide in the presence of free SG1 (N‐tert‐butyl‐N‐1‐diethylphosphono‐(2,2‐dimethylpropyl) nitroxide), with MAMA‐SG1 (N‐(2‐methylpropyl)‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐O‐(2‐carboxylprop‐2‐yl)hydroxylamine) alkoxyamine as initiator. The reactivity ratios of NAS and NVP were determined to be r_NAS = 0.12 and r_NVP = 0, indicating a strong alternating tendency for the P(NAS‐co‐NVP) copolymer. NAS/NVP copolymerization was then performed from a SG1‐functionalized poly(D ,L ‐lactide) (PLA‐SG1) macro‐alkoxyamine as initiator, leading to the corresponding PLA‐b‐P(NAS‐co‐NVP) block copolymer, with similar NAS and NVP reactivity ratios as mentioned above. The copolymer was used as a surface modifier for the PLA diafiltration and nanoprecipitation processes to achieve nanoparticles in the range of 450 and 150 nm, respectively. The presence of the functional/hydrophilic P(NAS‐co‐NVP) block, and particularly the N‐succinimidyl (NS) ester moieties at the particle surface, was evidenced by ethanolamine derivatization and zeta potential measurements. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

RGD peptide grafted biodegradable amphiphilic triblock copolymer poly(glutamic acid)‐b‐poly(L‐lactide)‐b‐poly(glutamic acid): Synthesis and self‐assembly

A novel amphiphilic biodegradable triblock copolymer (PGL‐PLA‐PGL) with polylactide (PLA) as hydrophobic middle block and poly(glutamic acid) (PGL) as hydrophilic lateral blocks was successfully synthesized by ring‐opening polymerization (ROP) of L ‐lactide (LA) and N‐carboxy anhydride (NCA) consecutively and by subsequent catalytic hydrogenation. The results of cell experiment of PGL‐PLA‐PGL suggested that PGL could improve biocompatibility of polyester obviously. The copolymer could form micelles of spindly shape easily in aqueous solution. The pendant carboxyl groups of the triblock copolymer were further activated with N‐hydroxysuccinimide and combined with a cell‐adhesive peptide GRGDSY. Incorporation of the oligopeptide further enhanced the hydrophilicity and led to formation of spherical micelles. PGL‐PLA‐PGL showed better cell adhesion and spreading ability than pure PLA and the GRGDSY‐containing copolymer exhibited even further improvement in cell adhesion and spreading ability, indicating that the copolymer could find a promising application in drug delivery or tissue engineering. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3218–3230, 2007     

Magnetic solid-phase extraction using magnetic hypercrosslinked polymer for rapid determination of illegal drugs in urine

A novel magnetic material Fe₃O₄/SiO₂/P(MAA‐co‐VBC‐co‐DVB) was prepared via the hypercrosslinking of its precursor which was produced via precipitation polymerization of methacrylic acid (MAA), vinylbenzyl chloride (VBC), and divinylbenzene (DVB) in the presence of Fe₃O₄/SiO₂ submicrospheres with the surface containing abundant reactive double bonds. The resultant sorbent was characterized by scan electron microscopy, N₂ adsorption, and Fourier transform infrared spectroscopy. It was found that this material had remarkable features such as large surface area (500 m²/g) and pore volume (0.32 cm³/g), as well as desirable chemical composition (including hydrophobic and ion‐exchange moieties). Taking advantages of the Fe₃O₄/SiO₂/P(MAA‐co‐VBC‐co‐DVB), a magnetic SPE (MSPE) coupled with capillary electrophoresis (CE) method was developed for the determination of illegal drugs in urine samples. The extraction time could be clearly shortened up to 3 min. The recoveries of these drug compounds were in the range of 84.0–123% with relative standard deviations ranging between 1.7 and 10.5%; the limit of detection was in the range of 4.0–6.0 μg/L. The proposed method is simple, effective, and low‐cost, and provides an accurate and sensitive detection platform for abused drug analysis.     

Lactic acid‐ and carbonate‐based crosslinked polymeric micelles for drug delivery

Our objective was to synthesize and evaluate lactic acid‐ and carbonate‐based biodegradable core‐ and core‐corona crosslinkable copolymers for anticancer drug delivery. Methoxy poly(ethylene glycol)‐b‐poly(carbonate‐co‐lactide‐co‐5‐methyl‐5‐allyloxycarbonyl‐1,3‐dioxane‐2‐one) [mPEG‐b‐P(CB‐co‐LA‐co‐MAC)] and methoxy poly(ethylene glycol)‐b‐poly(acryloyl carbonate)‐b‐poly(carbonate‐co‐lactide) [mPEG‐b‐PMAC‐b‐P(CB‐co‐LA)] copolymers were synthesized by ring‐opening polymerization of LA, CB, and MAC using mPEG as an macroinitiator and 1,8‐diazabicycloundec‐7‐ene as a catalyst. These amphiphilic copolymers which exhibited low polydispersity and critical micelle concentration values (0.8–1 mg/L) were used to prepare micelles with or without drug and stabilized by crosslinking via radical polymerization of double bonds introduced in the core and interface to improve stability. mPEG₁₁₄‐b‐P(CB₈‐co‐LA₃₅‐co‐MAC_2.5) had a higher drug encapsulation efficiency (78.72% ± 0.15%) compared to mPEG₁₁₄‐b‐PMAC_2.5‐b‐P(CB₉‐co‐LA₃₉) (20.29% ± 0.11%).¹H NMR and IR spectroscopy confirmed successful crosslinking (～70%) while light scattering and transmission electron microscopy were used to determine micelle size and morphology. Crosslinked micelles demonstrated enhanced stability against extensive dilution with aqueous solvents and in the presence of physiological simulating serum concentration. Furthermore, bicalutamide‐loaded crosslinked micelles were more potent compared to non‐crosslinked micelles in inhibiting LNCaP cell proliferation irrespective of polymer type. Finally, these results suggest crosslinked micelles to be promising drug delivery vehicles for chemotherapy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Cationic polymerization of L,L‐lactide

Cationic bulk polymerization of L ,L‐ lactide (LA) initiated by trifluromethanesulfonic acid [triflic acid (TfA)] has been studied. At temperatures 120–160 °C, polymerization proceeded to high conversion (>90% within ～8 h) giving polymers with M_n ～ 2 × 10⁴ and relatively high dispersity. Thermogravimetric analysis of resulting polylactide (PLA) indicated that its thermal stability was considerably higher than the thermal stability of linear PLA of comparable molecular weight obtained with ROH/Sn(Oct)₂ initiating system. Also hydrolytic stability of cationically prepared PLA was significantly higher than hydrolytic stability of linear PLA. Because thermal or hydrolytic degradation of PLA starting from end‐groups is considerably faster than random chain scission, both thermal and hydrolytic stability depend on molecular weight of the polymer. High thermal and hydrolytic stability, in spite of moderate molecular weight of cationically prepared PLA, indicate that the fraction of end‐groups is considerably lower than in linear PLA of comparable molecular weight. According to proposed mechanism of cationic LA polymerization growing macromolecules are fitted with terminal ? OH and ? C(O)OSO₂CF₃ end‐groups. The presence of those groups allows efficient end‐to‐end cyclization. Cyclic nature of resulting PLA explains its higher thermal and hydrolytic stability as compared with linear PLA. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2650–2658, 2010     

Preparation of a Hyper‐cross‐linked Polymer Monolithic Column and Its Application to the Sensitive Determination of Genomic DNA Methylation

A hyper‐cross‐linked polymer monolithic column, poly(methacrylatoethyl trimethyl ammonium‐co‐vinylbenzene chloride‐co‐divinylbenzene) (MATE‐co‐VBC‐co‐DVB) with phenyl and quaternary ammonium groups was successfully prepared in the current study. The prepared monolith possesses large specific surface area, narrow mesopore size distribution and high column efficiency. The poly(MATE‐co‐VBC‐co‐DVB) monolithic column was demonstrated to have strong anion exchange/reversed‐phase (SAX/RP) mixed‐mode retention for analytes on capillary liquid chromatography (cLC). By using this monolithic column, we developed a rapid and sensitive method for the detection of DNA methylation. Our results showed that six nucleobases (adenine, guanine, cytosine, thymine, uracil, and 5‐methylcytosine (5‐mC)) can be baseline separated within 15 min by electrostatic repulsion and hydrophobic interactions between nucleobases and the monolithic stationary phase. The limit of detection (LOD, signal/noise=3) of 5‐mC is 0.014 pmol and endogenous 5‐mC can be distinctly detected by using only 10 ng genomic DNA, which is comparable to that obtained by mass spectrometry analysis. Furthermore, by using the method developed here, we found that DNA methylation inhibitor 5‐azacytidine (5‐aza‐C) and 5‐aza‐2′‐deoxycytidine (5‐aza‐CdR) could induce a significant decrease of genome‐wide DNA methylation in human lung carcinoma cells (A549) and cervical carcinoma cells (HeLa).     

Facile preparation of core‐crosslinked micelles from azide‐containing thermoresponsive double hydrophilic diblock copolymer via click chemistry

Double hydrophilic diblock copolymer, poly(N,N‐dimethylacrylamide)‐b‐poly(N‐isopropylacrylamide‐co‐3‐azidopropylacrylamide) (PDMA‐b‐P(NIPAM‐co‐AzPAM), containing azide moieties in one of the blocks was synthesized via consecutive reversible addition‐fragmentation chain transfer polymerization. The obtained diblock copolymer molecularly dissolves in aqueous solution at room temperature, and can further supramolecularly self‐assemble into core‐shell nanoparticles consisting of thermoresponsive P(NIPAM‐co‐AzPAM) cores and water‐soluble PDMA coronas above the lower critical solution temperature of P(NIPAM‐co‐AzPAM) block. As the micelle cores contain reactive azide residues, core crosslinking can be facilely achieved upon addition of difunctional propargyl ether via click chemistry. In an alternate approach in which the PDMA‐b‐P(NIPAM‐co‐AzPAM) diblock copolymer was dissolved in a common organic solvent (DMF), the core‐crosslinked (CCL) micelles can be fabricated via “click” crosslinking upon addition of propargyl ether and subsequent dialysis against water. CCL micelles prepared by the latter approach typically possess larger sizes and broader size distributions, compared with that obtained by the former one. In both cases, the obtained (CCL) micelles possess thermoresponsive cores, and the swelling/shrinking of which can be finely tuned with temperature, rendering them as excellent candidates as intelligent drug nanocarriers. Because of the high efficiency and quite mild conditions of click reactions, we expect that this strategy can be generalized for the structural fixation of other self‐assembled nanostructures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 860–871, 2008     

Single‐chain nanoparticles with well‐defined structure via intramolecular crosslinking of linear polymers with pendant benzoxazine groups

Controlled intramolecular collapse of linear polymer chains with crosslinkable groups is an efficient way to prepare single‐chain nanoparticles in the size range of 5–20 nm. However, the nature of the crosslinking group is critical. In present study, poly(styrene‐co‐chloromethyl styrene) [P(St‐co‐CMS)] was synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization and then was converted into polystyrene azide (PS? N₃). Polystyrene containing benzoxazine side groups [P(St‐co‐BS)], which can be used as the precusor for the later intramolecular collapse, was obtained from PS? N₃ and 3‐(4‐(prop‐2‐ynyloxy)phenyl)‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazine (P‐APPE) via the method of click chemistry. The sub‐20 nm polymeric nanoparticles with well‐defined structure via thermally intramolecular crosslinking of P(St‐co‐BS) were prepared. The structure change from the linear polymers to the single‐chain nanoparticles was confirmed by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and gel permeation chromatography (GPC). The morphology and the dimension of the nanoparticles were characterized by using transmission electron microscope (TEM), atomic force microscopy (AFM), as well as dynamic light scattering (DLS). The results reveal that the size of the nanoparticles can be regulated by changing the molecular weight of the precursors and the amount of pendant benzoxazine groups by the use of controlled polymerization techniques. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Crosslinking‐induced morphology change of latex nanoparticles: A study of RAFT‐mediated polymerization in aqueous dispersed media using amphiphilic double‐brush copolymers as reactive surfactants

Amphiphilic double‐brush copolymers (DBCs) with each graft site quantitatively carrying both a hydrophilic poly(ethylene oxide) (PEO) graft and a hydrophobic polystyrene (PSt) graft are synthesized by sequential reversible addition‐fragmentation chain transfer (RAFT) polymerization and ring‐opening metathesis polymerization (ROMP). These DBCs are used as both surfactants and polyfunctional RAFT agents in the radical polymerization of St in aqueous dispersed media. Miniemulsions with narrowly dispersed St‐based nanodroplets are readily obtained after ultrasonication of the reaction mixtures. Without the presence of crosslinker, chain‐extension polymerization of St from the DBCs yields well‐defined polymeric latexes with narrow size distributions. However, with the presence of divinylbenzene (DVB) as the crosslinker, vesicular polymeric nanoparticles are formed as the major product. Such crosslinking‐induced change in morphology of the resulting latex nanomaterials may be ascribed to the increase of interfacial curvature in the heterophase systems during crosslinking polymerization. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3250–3259     

Friedel–crafts reactions of pendant vinyl groups in macroporous monosized poly(meta‐divinylbenzene) and poly(para‐divinylbenzene) particles

Residual vinyl groups in macroporous monosized polymer particles of poly(meta‐DVB) and poly(para‐DVB) prepared with toluene and 2‐EHA as porogens have been reacted with aluminum chloride as Friedel–Crafts catalyst with and without the presence of lauroyl chloride. In the reaction between aluminum chloride and pendant vinyl groups a post‐crosslinking by cationic polymerization takes place. A reaction occurring simultaneously is the addition of HCl to the double bonds. The progress of these reactions was studied by characterization of vinyl group conversion, pore size distribution, specific surface area, morphology, and swelling behavior. In the reaction with aluminum chloride the poly(para‐DVB) particles showed a substantially higher conversion of pendant vinyl groups than the particles made of poly(meta‐DVB) independent of porogen type. The reaction with aluminum chloride led to a reduced swelling in organic solvents and an increased rigidity of the particles prepared with toluene as porogen. This is confirmed by an increase in the total pore volume in the dry state and a change in the pore size distribution of these particles. Also in the reaction with lauroyl chloride poly(para‐DVB) particles have shown a higher conversion of pendant vinyl groups than poly(meta‐DVB) particles and the acylation was almost complete at the early stage of the reaction. The swelling in organic solvents is reduced as a result of the incorporation of acyl groups into the particles prepared with toluene as porogen. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1366–1378, 2000     

Synthesis and characterization of grafted/crosslinked proton conducting membranes based on amphiphilic PVDF copolymer

A novel graft copolymer consisting of a poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) backbone and poly(glycidyl methacrylate) side chains, that is, P(VDF‐co‐CTFE)‐g‐PGMA, was synthesized through atom transfer radical polymerization (ATRP) using CTFE units as a macroinitiator. Successful synthesis and microphase‐separated structure of the polymer were confirmed by ¹H NMR, FTIR spectroscopy, and TEM. As‐synthesized P(VDF‐co‐CTFE)‐g‐PGMA copolymer was sulfonated by sodium bisulfite, followed by thermal crosslinking with sulfosuccinic acid (SA) via the esterification to produce grafted/crosslinked polymer electrolyte membranes. The IEC values continuously increased with increasing SA content but water uptake increased with SA content up to 10 wt %, above which it decreased again as a result of competitive effect between crosslinking and hydrophilicity of membranes. At 20 wt % of SA content, the proton conductivity reached 0.057 and 0.11 S/cm at 20 and 80 °C, respectively. The grafted/crosslinked P(VDF‐co‐CTFE)‐g‐PGMA/SA membranes exhibited good mechanical properties (>400 MPa of Young's modulus) and high thermal stability (up to 300 °C), as determined by a universal testing machine (UTM) and TGA, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1110–1117, 2010     

Formation of porous polymer morphology by microsyneresis during divinylbenzene polymerization

This article describes the investigation of the importance of various reaction conditions on microsyneretic pore formation during polymerization of divinylbenzene (DVB) under so‐called “solvothermal” conditions. To induce microsyneretic pore formation, the most important parameter is an unusually high dilution of monomers with a “good” porogen solvating the polymer chains. High dilution and solvation of the growing poly(DVB) chains promote the prolongation of the polymer chains rather than their interconnection by crosslinking. Consequently, when the polymer gel density reaches the point where syneresis starts, the polymer network is geometrically too extensive to be broken up into precipitating entities and, instead, porogen droplets are formed within the continuous polymer gel. The pore geometry created by microsyneresis offers high surface area in wide mesopores and hence, high capacity for supporting functional groups or reactions with much better accessibility than narrow pores between polymer microspheres produced by macrosyneresis in conventional styrenic polymer supports. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 774–781     

Frontal polymerization for smart intrinsic self‐healing hydrogels and its integration with microfluidics

Frontal polymerization (FP) is applied for the synthesis of β‐cyclodextrin/poly(vinylimidazole‐co‐N‐vinylcaprolactam‐co‐acrylic acid) (β‐CD/P(VI‐co‐NVCL‐co‐AA)) copolymers. The dependence of frontal velocity and temperature on the initiator and cross‐linker are discussed. The synthesized copolymers have been characterized by Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The thermo‐pH dual‐stimuli responsive behavior of the hydrogel is determined by swelling measurement at different temperatures and pH values. Besides, the hydrogels show intrinsic self‐healing behavior and their healing efficiency is determined by the mechanical tests. Interestingly, we integrate FP with microfluidic technology, which may realize the execution of FP under continuous condition. Such simple microfluidics‐FP integrated approach has both methodological and practical value for the synthesis of functional materials. This paper mainly presents the synthesis and characterization of β‐cyclodextrin/poly(vinylimidazole‐co‐N‐vinylcaprolactam‐co‐acrylic acid) (β‐CD/P(VI‐co‐NVCL‐co‐AA)) copolymers by using thermal frontal polymerization (TFP). Hydrogels were found to be self‐healing with good mechanical performance and show dual thermo‐pH responsive behavior. Low‐cost, energy‐saving and efficient method of thermal frontal polymerization process was integrated with microfluidics technology to prepare supraball hydrogel. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1412–1423     

Facile synthesis of star‐shaped copolymers via combination of RAFT and ring opening polymerization

Reversible addition fragmentation chain transfer (RAFT) polymerization and bifunctional sparteine/thiourea organocatalyst‐mediated ring opening polymerization (ROP) were combined to produce poly(L ‐lactide) star polymers and poly(L ‐lactide‐co‐styrene) miktoarm star copolymers architecture following a facile experimental procedure, and without the need for specialist equipment. RAFT was used to copolymerize ethyl acrylate (EA) and hydroxyethyl acrylate (HEA) into poly(EA‐co‐HEA) co‐oligomers of degree of polymerization 10 with 2, 3, and 4 units of HEA, which were in turn used as multifunctional initiators for the ROP of L ‐lactide, using a bifunctional thiourea organocatalytic system. Furthermore, taking advantage of the living nature of RAFT polymerization, the multifunctional initiators were chain extended with styrene (poly((EA‐co‐HEA)‐b‐styrene) copolymers), and used as initiators for the ROP of L ‐lactide, to yield miktoarm star copolymers. The ROP reactions were allowed to proceed to high conversions (>95%) with good control over molecular weights (ca. 28,000‐230,000 g/mol) and polymer structures being observed, although the molecular weight distributions are generally broader (1.3–1.9) than those normally observed for ROP reactions. The orthogonality of both polymerization techniques, coupled with the ubiquity of HEA, which is used as a monomer for RAFT polymerization and as an initiator for ROP, offer a versatile approach to star‐shaped copolymers. Furthermore, this approach offers a practical approach to the synthesis of polylactide star polymers without a glove box or stringent reaction conditions. The phase separation properties of the miktoarm star copolymers were demonstrated via thermal analyses. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6396–6408, 2009     

Controllable synthesis of bio‐based polylactide diols using an organocatalyst in solvent‐free conditions

Controllable synthesis of bio‐based polylactide (PLA) diols was realized by the ring‐opening polymerization (ROP) of lactide (LA) in the presence of 1,4‐butanediol (BDO) using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) as an organocatalyst in solvent‐free conditions. The catalytic activity and conversion of LA could reach ∼1 kg g⁻¹ DBU and >97%, respectively, and the polymerization yielded polymers with narrow polydispersity index (PDI) (1.15–1.29). Interestingly, the number average molecular weight (M_n) of the obtained PLA diol was in excellent linear relation with the molar ratio of LA and BDO, and hence can be precisely controlled. The structure of the diol was clearly confirmed by ¹H and ¹³C NMR, FTIR, and MALDI‐TOF mass spectra, proving BDO as an initiation‐transfer agent to participate in the polymerization. Kinetic study of the ROP demonstrates a pseudo‐first‐order kinetic model and a controlled “living” nature. Notably, it is found that the glass transition temperature (T_g) of the diol significantly depends on the M_n. Furthermore, various chain transfer agents and organocatalysts can also be used to successfully synthesize well‐defined PLA diols. Especially, functional bio‐based dihydric alcohols such as 2,5‐furandimethanol (FDMO)‐initiated ROP in this system could result in fully bio‐based PLA diols with functionality. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 968–976