Synthesis and Characterization of Lactone Functional Macromonomers by End Group Deactivation and Their Use in Miktoarm Star Polymer

Newly designed miktoarm star-shaped copolymers made of poly[(benzyl methacrylate(BMA)-co-(ε-caprolacton)(CL)] and poly[(BMA-b-MMA-b-BMA)-co-ε-caprolacton)(CL)] were synthesized by combining ring-opening polymerization (ROP) of ε-caprolactone (CL) and poly(BMA) five membered lacton fuctionalized prepared via atom transfer radical polymerization (ATRP) of BMA, and ε-CL and P(BMA-b-MMA-b-BMA) dual functionalized diblock copolymer, in the presence of tin(II) bis(2-ethylhexanoate) (Sn(Oct)2). Although lactone ended poly(benzyl methacrylate) with ε-caprolactone monomer gave ring open polymerization by Sn(Oct)2, the macromonomer itself did not give any poly- merization The macromonomers, and the miktoarm star-shaped copolymers were analyzed by FT-IR and 1H-NMR spectroscopies and GPC (gel permeation chromatograph), Differential scanning calorimetry (DSC-50) and termo- gravimetric analysis (TGA-50). These copolymers exhibited the expected structure. The crystallization of star-shaped copolymers was studied by DSC. The results show that when the content of the BMA block increased, the Tm of the star-shaped block copolymer increased.

SYNTHESIS OF HETEROARM STAR POLYMERS COMPRISING POLY(4-METHYLPHENYL VINYL SULFOXIDE) SEGMENT BY LIVING ANIONIC POLYMERIZATION

A series of 3-arm ABC and AA＇B and 4-arm ABCD, AA＇BC and AA＇A＂B heteroarm star polymers comprising one poly（4-methylphenyl vinyl sulfoxide） segment and other segments such as polystyrene, poly（a-methylstyrene）, poly（4-methoxystyrene） and poly（4-trimethylsilylstyrene） were synthesized by living anionic polymerization based on diphenylethylene （DPE） chemistry. The DPE-functionalized polymers were synthesized by iterative methodology, and the objective star polymers were prepared by two distinct methodologies based on anionic polymerization using DPE-functionalized polymers. The first methodology involves an addition reaction of living anionic polymer with excess DPE-functionalized polymer and a subsequent living anionic polymerization of 4-methylphenyl vinyl sulfoxide （MePVSO） initiated from the in situ formed polymer anion with two or three polymer segments. The second methodology comprises an addition reaction of DPE-functionalized polymer with excess sec-BuLi and a following anionic polymerization of MePVSO initiated from the in situ formed polymer anion and 3-methyl-1,1-diphenylpentyl anion as well. Both approaches could afford the target heteroarm star polymers with predetermined molecular weight, narrow molecular weight distribution （Mw/Mn 〈 1.03） and desired composition, evidenced by SEC, 1H-NMR and SLS analyses. These polymers can be used as model polymers to investigate structure-property relationships in heteroarm star polymers.

Role of Hydrodynamic Interactions in the Deformation of Star Polymers in Poiseuille Flow

Stretching polymer in fluid flow is a vital process for studying and utilizing the physical properties of these molecules,such as DNA linearization in nanofluidic channels.We studied the role of hydrodynamic interactions(His)in stretching a free star polymer in Poiseuille flow through a tube using mesoscale hydrodynamic simulations.As increasing the flow strength,star polymers migrate toward the centerline of tube due to His,whereas toward the tube wall in the absence of His.By analyzing the end monomer distribution and the perturbed flow around the star polymer,we found that the polymer acts like a shield against the flow,leading to additional hydrodynamic drag forces that compress the arm chains in the front of the star center toward the tube axis and lift the arm chai ns at the back toward the tube wall.The balanced hydrodynamic forces freeze the polymer into a trumpet structure,where the arm chains maintain a steady strongly stretched state at high flow strength.In contrast,the polymer displays remarkably large conformational change when switching off His.Our simulation results explained the coupling between His and the structure of star polymers in Poiseuille flow.

Synthesis of Star Polymeric Ionic Liquids and Use as the Stabilizers for High Internal Phase Emulsions

A series of well-defined core cross-linked star （CCS） polymeric ionic liquids （PILs） were synthesized via a three- step approach. First, the styrenic imidazole-based CCS polymer （S-PVBnIm） was prepared by the RAFT-mediated heterogeneous polymerization in a water/ethanol solution, followed by the quaternization of S-PVBnIm with bromoalkanes and anion exchange. The CCS polymers were characterized by gel permeation chromatography （GPC）, nuclear magnetic resonance （NMR） spectroscopy, Fourier transform infrared spectroscopy （FTIR）, thermal gravimetric analysis （TGA）, and differential scanning calorimetry （DSC）. The obtained CCS polymers were used as the effective emulsifiers for oil-in-water high internal phase emulsions （HIPEs）. Multiple oils with different polarity including n-dodecane, undecanol, toluene and octanol were emulsified using 0.5 wt% S-PVBnIm aqueous solution under the acidic condition to form HIPEs with long-term stabilities. The excellent emulsification properties of CCS PILs were demonstrated by HIPE formation for a variety of oils. The properties of HIPEs in terms of emulsion type and oil droplet size were characterized by the confocal laser scanning microscopy （CLSM）. The intriguing capability of CCS PILs to stabilize HIPEs of various oils holds great potentials for the practical applications.

Molecular Dynamics Study of Star Polymer Melts under Start-up Shear

It has been established that star polymers with a large number of arms display both the conventional chain relaxation and a slower interchain relaxation due to the formation of hard cores,which is called the local structural relaxation.Here,we demonstrate that this unique relaxation property of multi-arm stars leads to unusual rheological behaviors.We study the response of star polymer melts with various arm numbers to start-up shear flow via nonequilibrium molecular dynamics simulation.Our simulation results indicate that the stress-strain response of multi-arm star polymer melts differs from that of star polymers with a small number of arms in both quantitative and qualitative manners.While the multi-arm star polymer melts exhibit an overshoot peak in the stress-strain curve both at relatively small and sufficiently large shear rates,two overshoot peaks appear when the flow strength is comparable to the relaxation time of the star polymers.This double stress overshoot is absent in linear polymers and star polymers with a small number of arms and is evidently related to the presence of the local structural relaxation in star polymers with a large number of arms.We present a detailed analysis of the conformational and dynamical properties of star polymer melts under start-up shear to gain a molecular understanding of their stress response.

A STEERED MOLECULAR DYNAMICS SIMULATION ON THE ELASTIC BEHAVIOR OF ADSORBED STAR POLYMER CHAINS

Elastic behavior of 4-branched star polymer chain with different chain length N adsorbed on attractive surface is investigated using steered molecular dynamics （SMD） simulation method based on the united-atom （UA） model for branched alkanes. The simulation is realized by pulling up the chain via a linear spring with a constant velocity v = 0.005 nm/ps. At the beginning, the chain lies extensionally on adsorbed surface and suffers continuous deformations during the tensile process. Statistical parameters as mean-square radii of gyration 〈S2〉xy, 〈S2〉z, shape factor 〈δ〉, describing the conformational changes, sectional density 〈den〉 which gives the states of the chain, and average surface attractive energy 〈Ua〉, average total energy 〈U〉, average force 〈f〉 probed by the spring, which characterize the thermodynamic properties, are calculated in the stimulant process. Remarkably, distinguishing from the case in linear chains that there only exists one long plateau in the curve of 〈f 〉, the force plateau in our study for star chains is multiple, denoting different steps of desorption, and this agrees well with the experimental results in essence. We find during the tensile process, there are three characteristic distances Zc, Zt and Z0 from the attractive surface, and these values vary with N. When Z = Zc, the chain is stripped from the surface, but due to the form of wall-monomer interaction, the surface retains weak influence on the chain till Z = Zc. From Z = Zt, parameters 〈Ua〉, 〈U〉 and 〈f〉 respectively reach a stable value, while the shape and the size of the chain still need adjustments after Zt till Zo to reach their equilibrium states. Specifically, for short chain of N = 41, Zt and Z0 are incorporated. These results may help us to deepen the knowledge about the elastic behavior of adsorbed star polymer chains.

Positioning a fluorescent probe at the core of a glassy star polymer for detection of local dynamics

Accessing local dynamics within a single macromolecule is the key to understand the physical origin of the viscoelasticity and especially the glass transition. In order to extract specific information on the dynamics of the branch point of a star polymer around its glass transition temperature, four-arm star poly （n-butyl methacrylate） with a fluorescent core was synthesized using perylene diimide as initiator and polymerization conducted via atom transfer radical polymerization. The process is found to be effective in positioning the fluorophore at the branch point with the fluorophore intact, which allows the successful application of single molecule fluorescence defocus imaging in examining the local site- sensitive dynamics. The power spectra of rotation trajectories, the population of rotating fluorophores as well as the distribution of angular displacement were used to revel the difference in local dynamics between branch point and the arm＇s end. It is discovered that the local dynamics at the core of the star polymer is much less activated than that at the arm＇s end. The results demonstrate the strong effect dues to the topological constrain at the branch point and the more free space at the arm＇s end.

AMPHIPHILIC STAR-BLOCK COPOLYMERS BY IODIDE-MEDIATED RADICAL POLYMERIZATION

Amphiphilic star-block copolymers composed of polystyrene and poly（acrylic acid） were synthesized by iodide- mediated radical polymerization. Firstly, free radical polymerization of styrene was carried out with AIBN as initiator and 1,1,1-trimethyolpropane tri（2-iodoisobutyrate） as chain transfer agent, giving iodine atom ended star-shaped polystyrene with three arm chains, R（polystyrene）3. Secondly, tert-butyl acrylate was polymerization using polystyrene obtained as macro-chain transfer agent, and star-block copolymer, R（polystyrene-b-poly（tert-butyl acrylate））3 with controlled molecular weight was obtained. Finally, amphiphilic star-block copolymer, R（polystyrene-b-poly（acrylic acid））3 was obtained by hydrolysis of R（polystyrene-b-poly（tert-butyl acrylate））3 under acidic condition.

Synthesis and characterization of star-comb styrene/butadiene copolymer

新奇星梳子苯乙烯 / 丁二烯共聚物(SC-SBC ) 被 anionic 聚合和 grafting 反应作为联合代理人与 epoxidized 星液体 polybutadiene (ESPB ) 综合。星梳子大分子的全面形状能被改变方面链的分子的重量和数字改变。分子的参数和 SC-SBC 树脂的机械性质被调查。SC-SBC 树脂的 notched izod 影响力量是优秀的并且至于 239 J/m 作为高度到达。

PREPARATION OF STAR NETWORK PEG-BASED GEL POLYMER ELECTROLYTES FOR ELECTROCHROMIC DEVICES

An amorphous,colorless,and highly transparent star network polymer with a pentaerythritol core linking four PEG-block polymeric arms was synthesized from the poly(ethylene glycol)(PEG),pentaerythritol,and dichloromethane by Williamson reaction.FTIR and ~1H-NMR measurement demonstrated that the polymer repeating units were C[CH_2-OCH_2O-(CH_2CH_2O)_m-CH_2O-(CH_2CH_2O)_n-CH_2O]_4.The polymer host held well mechanical properties for pentaerythritol cross-linking.The gel polymer electrolytes based on Lithium pe...

Synthesis and characterization of miktoarm star copolymer of styrene and butadiene using multifunctional macromolecular initiator

A new kind of multifunctional macromolecular initiator with Sn-C bonds and polydiene arms was synthesized by living anionic polymerization. At first, polydiene-stannum chloride （PD-SnCl3） was prepared by the reaction of n-butyl-Li （n-BuLi）, stannic chloride （SnCl4） and diene. Then PD-SnCl3 was used to react with the dilithium initiator to prepare the multifunctional organic macromolecular initiators. The result suggested that the initiators had a remarkable yield by GPC, nearly 90%. By using these multifunctional macromolecular initiators, styrene and butadiene were effectively polymefized via anionic polymerization, which gave birth to novel miktoarm star copolymers. The relative molecular weight and polydispersity index, microstructure contents, copolymerization components, glass transition temperature （Tg） and morphology of the miktoarm star copolymers were investigated by GPC-UV, ~H NMR, DSC and TEM, respectively. 2009 Xing Ying Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

SYNTHESIS OF HETEROARM STAR-SHAPED POLYMER BY THE USE OF POLYFUNCTIONAL CHAIN-TRANSFER AGENT via CONVENTIONAL FREE RADICAL POLYMERIZATION

Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent.In the first step,free radical polymerization of methyl methacrylate was carried out in the presence of a polyfunctional chain transfer agent,pentaerythritol tetrakis(3-mercaptopropinate).At appropriate monomer conversions,two-arm PMMA having two residual thiol groups at the chain center or three-arm PMMA having one residual thiol group at the core were o...

Synthesis and Characterization of Star-branched Polyisobutylene by Combination of Anionic Polymerization and Cationic Polymerization

A star-shaped multifunctional styrene-isoprene copolymer was synthesized with n-BuLi as initiator, divinyl benzene as coupling agent, cyclobexane as solvent by living anionic polymerization. Using this polymer as grafting agent, a novel star-shaped branched polymer, containing several polyisobutylene, was prepared via cationic ~aolymerization. The star PS-b-PI and star-branched polyisobutylene were characterized by GPC, ＇HNMR and FT-IR, and the effects of different adding order and the amount of grafting agent were investigated.

Synthesis and performance of miktoarm star copolymers of styrene and butadiene

A novel multifunctional macromolecular organolithium initiator （PD-Sn-（RLi）3） was prepared via living anionic polymerization and used for the synthesis of miktoarm star copolymers in cyclohexane. The average molecular weight, polydispersity index, microstructure and unit composition of the miktoarm star copolymers were characterized with GPC and 1H-NMR. Performances of the miktoarm star styrene-butadiene rubbers were investigated in comparison with those of the blend rubbers such as the tin-coupled star-shaped random copolymers of styrene-butadiene rubber（S-SBR）/natural rubber （NR） blend rubber and S-SBR/Cis-1, 4-polybutadiene rubber （Cis-BR） blend rubber.

线形聚(ε-己内酯)和星形聚(ε-己内酯)的合成及表征

以辛酸亚锡Sn(Oct)2为催化剂,分别通过苯甲醇和季戊四醇引发ε-己内酯(CL)的开环聚合(ROP),制备了线形聚(ε-己内酯)(PCL)和四臂星形聚(ε-己内酯)(S-(PCL)4)。用核磁共振氢谱(1H NMR)表征了聚合物的结构,用凝胶渗透色谱(GPC)测定了它们的相对分子质量。线形聚(ε-己内酯)(PCL)和四臂星形聚(ε-己内酯)(S-(PCL)4)可用后续制备基于聚己内酯的两亲性嵌段共聚物,为可生物降解药物输送载体的开发和应用打下基础。

基于δ-己内酯的多臂星形热塑性弹性体的合成和性质

以生物基单体δ-己内酯(δCL)和L-丙交酯(L-LA)为原料,以三羟甲基丙烷或季戊四醇为引发剂,通过一锅法顺序加料方式制备了具有明确结构的(PδCL-b-PLLA)n多臂星形嵌段共聚物。使用小角X射线散射表征了(PδCL-b-PLLA)n的微相分离结构。通过单轴拉伸和循环拉伸实验,研究了拓扑结构对(PδCL-b-PLLA)n多臂星形嵌段共聚物力学性能的影响。结果表明:在分子量相同的情况下,星形嵌段共聚物具有比相应的ABA线形嵌段共聚物更高的断裂强度、弹性回复率以及更低的残留应变;与四臂星形嵌段共聚物相比,三臂星形嵌段共聚物表现出更好的拉伸性和弹性回复性。

Synthesis and characterization of star-comb polybutadiene and poly(ethylene-co-butene)

A novel star-comb polybutadiene(SC-PB) was synthesized with n-butyllithium(n-BuLi) as initiator,epoxidized star liquid polybutadiene(ESPB) as coupling agent,cyclohexane as solvent by living anionic polymerization and grafting-onto technology. The SC-PB was subsequently hydrogenated by homogeneous catalysis(catalytic hydrogenation using nickel naphthenate/ triisobutyl aluminum),to transform the SC-PB into the corresponding star-comb poly(ethylene-co-butene)(SC-PEB).The SC-PB was characterized by SEC-TALLS,~1...

SYNTHESIS,CHARACTERIZATION AND NANOPARTICLE FORMATION OF STAR-SHAPED POLY(L-LACTIDE)WITH SIX ARMS

Well-defined star-shaped poly(L-lactide)with six arms(sPLLA)was synthesized via the ring-opening polymerization of L-lactide using dipentaerythritol as initiator and stannous octoate as catalyst in bulk at 125~C.The effects of molar ratios of both monomer to initiator and monomer to catalyst on the molecular weights of as-synthesized sPLLA polymers were in detail investigated.The molecular weights of sPLLA polymers linearly increased with the molar ratio of monomer to initiator,and the molecular weight dist...

Precision Synthesis of End-Functionalized Star Poly(vinyl alcohol)s by RAFT Polymerization and Post-polymerization Modification

Poly(vinyl alcohol)(PVA)has been widely used in industrial and consumer products.In this study,we aimed to address this challenge by synthesizing well-defined multiarm poly(vinyl acetate)(PVAc)through the use of nonhydrolyzable vinyl ethertype multifunctional RAFT agents.The control over molecular weights was achieved by the RAFT process to afford polymers with dominant head-to-head linkages at the terminal.Especially,quantitative end-functionalization of the synthesized PVAc was performed using Michael thiol−ene or disulfide exchange reactions.Consequently,saponification of the PVAc enabled the synthesis of end-functionalized multiarm PVA in an efficient manner.This straightforward approach afforded well-defined functional PVAs,which enable further chemical modification,thus widening the utility of PVA in a range of applications,such as precisely controlled network synthesis and bioconjugation.

基于星型单体与RAFT相结合的超支化聚合物的合成与评价

为改变线性聚合物分子链长,高温下易剪切断链,抗温抗盐能力不足等缺点,在单体及组成一定的情况,通过改变聚合物的分子构象,采用可逆加成-断裂链转移聚合(RAFT)法,基于星型单体与RAFT相结合制备得到黏度效应低、抗温抗盐能力强的超支化聚合物EHBPS-P。性能评价结果表明,EHBPS-P抗温可达220℃,加入超支化聚合物的基浆在220℃老化后黏度降低率为66.7%(同组分线性聚合物黏度降低率达90.98%),淡水、盐水、复合盐水基浆中加量为1.0%(质量分数)时,可使钻井液的滤失量控制在10.0 mL以内,优于线性聚合物,有较好持续抗温性和长效的作用周期。