星状支化PS的合成与表征

利用原子转移自由基聚合方法,以α-溴代苯乙烷为引发剂,CuBr／2,2'-联二吡啶作为催化体系,合成星状支化聚苯乙烯(PS)。引发二苯甲烷双马来酰亚胺／苯乙烯电荷转移络合物体系就地优先生成多官能团引发剂,再引发苯乙烯聚合。采用核磁共振、凝胶渗透色谱、多角度激光散射和特性黏数等分析方法对聚合过程、聚合物结构、聚合物相对分子质量及其分布进行分析与表征。由多角度激光散射法测定的绝对重均分子量是由凝胶渗透色谱测定的4倍左右,相同相对分子质量的线型PS的特性黏数是星状PS的20倍,证实聚合产物确实具有支化结构。     

Controlled radical polymerization of p-(iodomethyl)styrene—a route to branched and star-like structures

p-(Iodomethyl)styrene was polymerized under the action of a radical initiator (AIBN). The polymerization proceeds with degenerative chain transfer and leads to well defined branched polymers with functional primary and secondary iodomethyl groups as revealed by NMR studies. The obtained polymer can be further used as macroinitiator for radical polymerization of styrene. This polymerization proceeds in controlled way to polystyrene star polymers with reactive groups at the end of their arms. The characterization of branched and star structures was performed by NMR and GPC with absolute molar mass detection (MALLS).     

Synthesis of star-shaped polymers by coupling reaction between multifunctional core and terminal functionalized polymers

Star-shaped polymers that consist of well-defined polystyrene (PS) arms were successfully synthesized in high yield by coupling reaction between multifunctional core molecules and hydroxyl-terminated PS in the presence of 1, 3-dicyclohexylcarbodiimide and 4-(dimethylamino) pyridine at room temperature. Several systems were investigated: (1) Pyromellitic dianhydride (PMDA) and hydroxyl-terminated PS (PS-OH) with narrow molecular weight distribution, which was prepared by atom transfer radical polymerization (ATRP) of St with 2-hydroxyethyl bromoisobutylate (HEBiB) as initiator. (2) PMDA and PS-OH prepared by conventional free radical polymerization, with 2-mercaptoethanol as chain transfer agent. (3) Narrow molecular weight distributed alternating copolymer of maleic anhydride (MA) and styrene (St), which was obtained via reversible addition fragmentation chain transfer polymerization (RAFT) process, and PS-OH obtained by ATRP. The formation of star-shaped PSs was confirmed by proton nuclear magnetic resonance (¹H NMR) and gel permeation chromatography (GPC).     

Initiator‐fragment incorporation radical polymerization of ethylene glycol dimethacrylate in the presence of 1,1‐diphenylethylene: synthesis and characterization of soluble hyperbranched polymer nanoparticles

The polymerization of ethylene glycol dimethacrylate (EGDMA) as crosslinker was carried out at 70 and 80 °C in benzene using dimethyl 2,2′‐azobisisobutyrate (MAIB) as initiator at concentrations as high as 0.50–0.70 mol l^?1 in the presence of 1,1‐diphenylethylene (DPE), where the concentrations of EGDMA and DPE were 0.50–0.70 and 0.25–0.50 mol l^?1, respectively. The polymerization proceeded homogeneously, without gelation, to give soluble polymers. The yield and molecular weight of the resulting polymers increased with time. The homogeneous polymerization system involved ESR‐observable DPE‐derived radicals of considerably high concentration (3.6–5.3 × 10^?5 mol l^?1). The methoxycarbonylpropyl groups as MAIB‐fragments were incorporated as a main constituent (35–50 mol%) into the polymers (initiator‐fragment incorporation radical polymerization). The polymers also contained DPE units (15 mol%) and EGDMA units with double bonds (10–25 mol%) and without double bonds (20 mol%). Results from gel permeation chromatography (GPC)–multiangle laser light scattering (MALLS), transmission electron microscopy (TEM) and viscometric measurements revealed that the individual polymer molecules were formed as hyperbranched nanoparticles. Copyright © 2004 Society of Chemical Industry     

Preparation of hyperbranched copolymers of maleimide inimer and styrene by ATRP

Novel hyperbranched copolymers were prepared by the atom transfer radical copolymerization of N-(4-α-bromobutyryloxy phenyl) maleimide (BBPMI) with styrene in 1-methyl-2-pyrrolidone (NMP) using the complex of CuBr/2,2′-bipyridine as catalyst. The copolymerization behavior was investigated by comparison of the conversion of double bond of BBPMI determined by ¹H NMR with that of styrene. The hyperbranched structure of resulting copolymers was verified by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS). The influences of dosage of catalyst and monomer ratio on the polymerization rate and structure of the resulting polymers were also investigated. The glass transition temperature of the resulting hyperbranched copolymer increases with increasing mole fraction of BBPMI, f_BBPMI. The resulting copolymers exhibit improved solubility in organic solvents; however, they show lower thermal stabilities than their linear analogues.     

原位生成自引发单体合成支化共聚物

以α-溴代异丁酸叔丁酯为引发剂,二乙烯苯为支化单体,苯乙烯为共聚单体,经原子转移自由基聚合原位生成自引发单体合成支化共聚物。用核磁共振法、凝胶渗透色谱法、三角激光散射法分别对聚合过程和聚合物进行了表征。结果表明：由于苯乙烯的引入,反应体系的交联得到了很好的控制,所得聚合物为支化结构。     

Synthesis of poly(epichlorohydrin‐g‐methyl methacrylate) graft copolymers by the combination of cationic and atom transfer radical polymerization

Poly(epichlorohydrin) possessing chloromethyl side groups in the main chain was used in the atom transfer radical polymerization of methyl methacrylate and styrene to yield poly(epichlorohydrin‐g‐methyl methacrylate) and poly(epichlorohydrin‐g‐styrene graft copolymers. The polymers were characterized by ¹H NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, and fractional precipitation method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2725–2729, 2006     

Modeling of “living” free‐radical polymerization processes. I. Batch,semibatch, and continuous tank reactors

A comprehensive mathematical model is developed for “living” free‐radical polymerization carried out in tank reactors and provides a tool for the study of process development and design issues. The model is validated using experimental data for nitroxide‐mediated styrene polymerization and atom transfer radical copolymerization of styrene and n‐butyl acrylate. Simulations show that the presence of reversible capping reactions between growing and dormant polymer chains should boost initiation efficiency when using free nitroxide in conjunction with conventional initiator and also increase the effectiveness of thermal initiation. A study shows the effects of the value of the capping equilibrium constant and capping reaction rate constants for both nitroxide‐mediated styrene polymerization (using alkoxyamine as polymer chain seeds) and atom transfer radical polymerization of n‐butyl acrylate (using methyl 2‐bromopropionate as chain extension seeds). Also the effect of introducing additional conventional initiator into atom transfer radical polymerization of n‐butyl acrylate is studied. It is found that the characteristics of long chain growth are determined by the fast exchange of radicals between growing and dormant polymer chains. Polymerization results in batch, semibatch, and a series of continuous tank reactors are analyzed. The simulations also show that a semibatch reactor is most flexible for the preparation of polymers with controlled architecture. For continuous tank reactors, the residence time distribution has a significant effect on the development of chain architecture. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1630–1662, 2002     

Preparation of heat‐resistant branched poly(styrene‐alt‐NPMI) by ATRP with divinylbenzene as the branching agent

Heat‐resistant branched poly(styrene‐alt‐NPMI) has been prepared via atom transfer radical polymerization (ATRP) of styrene (St) and N‐phenyl maleimide (NPMI) with divinylbenzene (DVB) as the branching agent in anisole at 80°C. Gas chromatography (GC) was used to determine the conversion of the reactants. Triple detection gel permeation chromatography (TD‐GPC) was used to analyze the copolymers. The results show that the polymerization yields primary chains predominately in the early stages and the formation of branched molecules occurs mainly when conversion is higher than 50%. As expected, higher dosage of DVB in our investigation range favors the formation of polymers with higher degree of branching. All the resulting branched poly(styrene‐alt‐NPMI)s have glass transition temperature (T_g) above 175°C, extrapolated initial weight loss temperature (T_i) above 410°C and statistic heat‐resistant index above 200°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of hyperbranched polymers through ATRP of in situ formed AB* monomer

The self‐condensing vinyl polymerization of an AB* monomer formed in situ by atom transfer radical addition from divinylbenzene (DVB) and (1‐bromoethyl)benzene (BEB) using atom transfer radical polymerization technique was studied. The catalyst concentration has a dramatic effect on polymerization. To study the polymerization mechanism and to achieve high molecular weight polymer, the polymerization was carried out in bulk with a catalyst to monomer ratio, 2,2′‐bipyridine to DVB, of 0.2 at 90°C. Proton nuclear magnetic resonance (¹H NMR) spectroscopy and size‐exclusion chromatography coupled with multiangle laser light scattering were used to analyze the polymerization aliquots and the obtained polymer. The intrinsic viscosities of the prepared polymers were also measured. Experimental results, from the comparison of the apparent molecular weights measured by size‐exclusion chromatography with the absolute values measured by multiangle laser light scattering as well as viscosity measurements, indicate the existence of hyperbranched structures in the prepared polymers. In sharp contrast to hyperbranched polymers from AB* monomer preprepared, hyperbranched ploy(divinylbenzene) prepared at equimolar amount of DVB and BEB has numerous residual pendant vinyl groups rather than only one double bond at its focal point. The hyperbranched polymers show relatively narrow molecular weight distribution (2.13–3.77) and exhibit excellent solubility in common organic solvents such as acetone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 850–856, 2006     

Aliphatic polyamidoamine hyperbranched polymers/layered silicate nanocomposites

Polyamidoamine hyperbranched polymer (Hyp)/clay nanocomposites were synthesized by using both of montmorillonite and laponite clays. Poly amidoamine hyperbranched polymer (Hyp) was prepared by one‐pot polymerization via couple monomer methodology. Afterward, the amino ends of Hyp were modified with methyl methacrylate (MMA), styrene (St) and butyl methacrylate (n‐BuMA) polymers which were previously prepared via ATRP (atom transfer radical polymerization) to form the corresponding new hyperbranched polymers Hyp₁, Hyp₂ and Hyp₃. Those formed polymers were inserted into the modified clay, such as montmorillonite and laponite to form their nanocomposites. The formed polymer/clay nanocomposites were characterized via XRD, TEM, and thermal analyses. The formed hyperbranched polymers generally showed intercalation behavior more than the exfoliation one mostly because of the bulkiness of the hyperbranched skeleton. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of aromatic carboxyl functionalized polymers by atom transfer radical polymerization

The synthesis of aromatic carboxyl functionalized polymers by atom transfer radical polymerization is described. The α‐bromo‐p‐toluic acid ( 1 ) initiated polymerization of styrene in the presence of copper(I) bromide and 2,2′‐bipyridyl affords quantitative yields of the corresponding aromatic carboxyl functionalized polystyrene ( 2 ). Polymerization proceeded via a controlled free radical process to afford quantitative yields of the corresponding aromatic carboxyl functionalized polymers with predictable molecular weights (M_n = 1600–25 900 g mol⁻¹), narrow molecular weight distribution (M_w /M_n = 1.1–1.40) and an initiator efficiency above 0.87. The polymerization process was monitored by gas chromatographic analysis. The functionalized polymers were characterized by thin layer chromatography, size exclusion chromatography, spectroscopy, potentiometry and elemental analysis. © 2000 Society of Chemical Industry     

Synthesis of well‐defined glycoconjugate polyacrylamides via preactivated polymers prepared by ATRP

Poly(N‐acryloxysuccinimide) (polyNAS) with narrow molecular weight distributions (MWD) applicable for the preparation of well‐defined glycoconjugate polyacrylamides were successfully prepared by atom transfer radical polymerization (ATRP). The structures of polyNAS were characterized by ¹H‐NMR and GPC. GPC results showed that the molecular weight polydispersity indices (PDI) range from 1.17 to 1.29. The molecular weights could be calculated based on ¹H‐NMR results but GPC results of polyNAS by using 0.01M LiBr/DMF did not give accurate molecular weights, probably because of the complex interaction in the system. The effects of free N‐hydroxysuccimide produced in the polymerization processes on the free‐radical concentrations and apparent initiation efficiencies of ATRP were discussed. Well‐defined glycoconjugate polyacrylamides (i.e., with narrow molecular weight distributions and designed glycoconjugate degrees) were prepared by substituting N‐oxysuccimide units with galactosamine followed by reaction of ethanolamine. The galactose conjugate degrees were determined by ¹H‐NMR and the total substitutions of N‐oxysuccimides were verified by ¹H‐NMR and FTIR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 189–194, 2005     

Primary amine functionalized polystyrenes by atom transfer radical polymerization

Primary amine functionalized polystyrenes were prepared in quantitative yields by atom transfer radical polymerization using the adduct of 1‐(bromoethyl)benzene with 1‐(4‐aminophenyl)‐1‐phenylethylene as initiator for styrene polymerization in the presence of a copper(I) bromide/N,N,N′,N′,N″‐pentamethyldiethylenetriamine catalyst system. The polymerizations proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding primary amine functionalized polystyrenes with predictable molecular weights (M_n = 2 × 10³ to 10 × 10³ g mol^?1), relatively narrow molecular weight distributions (M_w/M_n = 1.03–1.49), well defined chain‐end functionalities and initiator efficiencies as high as 0.92. The polymerization process was monitored by gas chromatographic analysis. The primary amine functionalized polymers were characterized by thin layer chromatography, size exclusion chromatography, potentiometry and spectroscopy. Experimental results are consistent with quantitative functionalization via the 1,1‐diphenylethylene derivative. Polymerization kinetic measurements show that the polymerization reaction follows first order rate kinetics with respect to monomer consumption and the number average molecular weight increases linearly with monomer conversion. © 2003 Society of Chemical Industry     

Synthesis of poly(ethylene glycol-b-styrene) block copolymers by reverse atom transfer radical polymerization

Reverse atom transfer radical polymerization (RATRP) of styrene (S) was carried out in bulk using polyazoester prepared by the reaction of polyethylene glycol with molecular weight of 3000 and 4,4′-azobis(4-cyanopentanoyl chloride) as initiator and CuCl₂/2,2′-bipyridine (bpy) catalyst system to yield poly(ethylene glycol-b-styrene) block copolymer. The block copolymers were characterized ¹H NMR, FT-IR spectroscopy and GPC. The ¹H NMR, and FT-IR spectra showed that formation of poly(ethylene glycol-b-styrene) block copolymer. The polydispersities of block copolymers were observed between from 1.49 and 1.98 GPC measurements.     

Preparation of dendron-like polystyrenes from atom transfer radical polymerization (ATRP) and direct chain-end functionalization

Dendron-like branched polystyrenes are prepared using atom transfer radical polymerization (ATRP) and chain-end functionalization. The growing chain ends of polystyrene from ATRP are end-capped with 1,4-benzoquinone to incorporate branching points and ATRP initiating groups to the chain ends. Sequential ATRP of styrene initiated from the chain ends builds up the polystyrene arms. The number-averaged molecular weights of the first, second, and third generations of dendron-like polystyrene polymers calculated from their respective ¹H NMR spectra are 5960, 6850, and 9150 g/mol, respectively. The NMR-data are consistent with the molecular weights determined by GPC. An approach to prepare dendron-like polymers through ATRP and chain-end functionalization is developed.     

A new synthetic approach to asymmetric amphiphilic ABA′ block copolymers by ATRP and click reactions

Well‐defined asymmetric amphiphilic ABA′ block copolymers composed of poly(ethylene oxide) monomethylene ether (MPEO) with different molecular weights as A or A′ block and poly(styrene) (PS) as B block were synthesized by the combination of atom transfer radical polymerization (ATRP) and click reactions. First, bromine‐terminated diblock copolymer poly(ethylene oxide) monomethylene ether‐block‐poly(styrene) (MPEO‐PS‐Br) was prepared by ATRP of styrene initiated with macroinitiator MPEO‐Br, which was prepared from the esterification of MPEO and 2‐bromoisobutyryl bromide. Then, the azido‐terminated diblock copolymers MPEO‐PS‐N₃ were prepared through the bromine substitution reaction with sodium azide. Propargyl‐terminated MPEO with a different molecular weight was prepared under the basic condition from propargyl alcohol and p‐toluenesulfonyl‐terminated MPEO, which was prepared through the esterification of MPEO and p‐toluenesulfochloride using pyridine as solvent. Asymmetric amphiphilic ABA′ block copolymers, with a wide range of number–average molecular weights from 1.92 × 10⁴ to 2.47 × 10⁴ and a narrow polydispersity from 1.03 to 1.05, were synthesized via a click reaction of the azido‐terminated diblock copolymers and the propargyl‐terminated MPEO in the presence of CuBr and 1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) catalyst system. The structures of these ABA′ block copolymers and corresponding precursors were characterized by NMR, IR, and GPC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and Characterization of Dumbbell Type Amphiphilic Block Copolymers via ATRP

Summary Dumbbell type amphiphilic block copolymers, two polymeric globules connected with poly(ethylene glycol) 2000 or 4000 (PEG 2k, PEG 4k), were synthesized and characterized. The outer polystyrene globules are hyperbranched poly(chloromethyl styrene) synthesized via atom transfer radical polymerization. The degree of branch of the hyperbranched polymer tells that the structure is rather closer to a dendrimer than a general hyperbranched polymer. The synthesized polymers have well controlled structures. The molecular weights and its distributions were chatacterized by GPC and 1H-NMR. The synthesized polymers were micellized in water using dialysis method and critical micelle concentration was measured using pyrene fluorescence method.     

Synthesis and characterization of a novel liquid crystalline star‐shaped polymer based on α‐CD core via ATRP

Well‐defined side‐chain liquid crystalline star‐shaped polymers were synthesized with a combination of the “core‐first” method and atom transfer radical polymerization (ATRP). Firstly, the functionalized macroinitiator based on the α‐Cyclodextrins (α‐CD) bearing functional bromide groups was synthesized, confirmed by ¹H‐NMR, MALDI‐TOF, and FTIR analysis. Secondly, the side‐chain liquid crystalline arms poly[6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate] (PMMAzo) were prepared by ATRP. The characterization of the star polymers were performed with ¹H‐NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM). It was found that the liquid crystalline behavior of the star polymer α‐CD‐PMMAzo_n was similar to that of the linear homopolymer. The phase‐transition temperatures from the smectic to nematic phase and from the nematic to isotropic phase increased as the molecular weight increased for most of these samples. All star‐shaped polymers show photoresponsive isomerization under the irradiation with Ultraviolet light. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Studies on the development of branching in ATRP of styrene and acrylonitrile in the presence of divinylbenzene

Branching atom transfer radical polymerization (ATRP) of styrene and acrylonitrile was attempted in the presence of divinylbenzene targeting toward soluble branched copolymer. The kinetics and the development of branching with monomer conversion were studied in detail. Gas chromatography (GC), gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS), proton nuclear magnetic resonance (¹H NMR) spectroscopy and intrinsic viscosity determination were used to monitor the polymerization process and characterize the obtained copolymer. Analysis of conversion of reactants, the growth manner of molecular weight with monomer conversion and GPC traces proved that the primary chains with low polydispersity formed mainly at the early stage and then were linked in a statistical manner to start the branching at the middle or late stage. The more the branching agent was used, the earlier the branching occurred, and too much higher level of branching agent resulted in gelation. For the selected ratio of [t-BBiB]/[DVB]/[St]/[AN] = 1/0.9/15/15, with monomer conversion less than 40%, primary chains with low polydispersity formed from the polymerization of St, AN and DVB, and only a part of the primary chains contained pendent vinyl group. When monomer conversion was up to 40%, the pendent vinyl groups participated in polymerization, resulting in the linking of the primary chains statistically to start the branching. The branching became significant at monomer conversion up to 50%, giving rise to a steep increase in molecular weight and width in molecular weight distribution. As the polymerization proceeded, the polymer composition gradually approached the feed composition, identifying the obtained branched copolymer provided some gradients are in its primary chains. Finally, branched copolymer bearing about six primary chains was prepared at monomer conversion near to 80%, its absolute weight average molecular weight was about 8.87 × 10⁴.