星形支化合成橡胶的合成与应用

从结构与性能的关系出发,介绍了星形支化结构改善合成橡胶加工性能的原理,对比分析了星形支化橡胶合成采用的先臂后核法、先核后臂法和核臂同时法的技术特点,总结了支化聚合物支化因子和平均臂数的表征方法,综述了不同合成橡胶胶种在星形支化方面取得的研究及应用进展。指出在星形支化合成橡胶新技术及新产品开发中,要结合现有橡胶和聚烯烃工业的主要原料,如苯乙烯、异戊二烯和丁二烯等共轭烯烃,设计合成新的支化剂,并以此开发星形支化合成橡胶。     

星形聚合物的最新研究进展

星形聚合物作为一种非线性聚合物,具有广阔的理论研究意义和工业应用前景,其结构、形态、合成与功能都是高分子科学领域中的热点问题。本文主要综述了均臂星形聚合物、杂臂星形聚合物、树状或支化结构星形聚合物的最新研究进展。     

以二乙烯基苯为核的星形支化聚异丁烯的制备与表征

采用活性正离子聚合法,以2-氯-2,4,4-三甲基戊烷/四氯化钛为引发剂体系,一氯甲烷/环己烷(体积比50/50)为溶荆,在-80℃下合成了以二乙烯基苯为核、聚异丁烯(PIB)为臂的星形支化聚合物.考察了聚合物的臂长和核大小对星形支化PIB的影响,并对聚合物的结构进行了表征.结果表明,核的增大和聚合时间的延长,有利于接枝聚合反应的进行和星形支化聚合物的形成;聚合物分子在四氢呋喃稀溶液中的幂指数为0.14,说明该聚合物具有支化结构.     

一种新型丁基橡胶淤浆稳定剂的合成与测评

通过负离子聚合技术,合成了一种星形聚苯乙烯-异戊二烯嵌段共聚物,并把它作为丁基橡胶的淤浆稳定剂和支化剂进行了测评。结果表明,合成的星形嵌段聚合物用量为0.5%～3%时,有稳定丁基橡胶淤浆的作用,且随着星形聚合物量的增加,淤浆稳定效果愈好,产品的相对分子质量分布愈宽;超出这个范围,有凝胶产物生成。     

支化聚合物的合成及表征

支化聚合物由于其独特的结构和性能以及可实现规模化生产的特点,已迅速成为一类重要的和具有广阔应用潜力的高分子材料。本文综述了近年来制备支化聚合物常用的合成方法：主链引发法、主链-支链偶联法以及单体-大分子单体共聚法;介绍了表征支化聚合物支化度的方法：红外光谱法、核磁共振法、差热分析法、GPC和自动粘度计联用法,并评价了各种方法的优缺点,目的在于加深人们对该领域的了解,从而促进该领域的快速发展。     

熔融缩聚法制备星形支化聚乳酸

以L-乳酸为原料,季戊四醇为支化剂,使用氯化亚锡和对甲苯磺酸复合催化剂,采用熔融缩聚法合成了星形支化聚乳酸.探讨了支化剂用量、催化剂用量、反应温度和时间等条件对星形支化聚乳酸特性黏数的影响.结果 表明,n(LLA)/n(PET)=1500,催化剂snCl2和对甲苯磺酸用量为单体L-乳酸质量的0.5%,聚合温度为180℃,体系压力为1.5kPa时熔融缩聚12 h,可得到特性黏数为0.634 dL/g的星形聚乳酸.采用凝胶渗透色潜-十八角激光散射仪、黏度计测定了聚合物的摩尔质量、均方旋转半径和特性黏数[η],并证明了支化结构的存在.最后,采用DSC、TG研究了星形聚乳酸的热性能.     

支化聚合物复鞣填充剂的制备与应用

以甘油(Gly)和马来酸酐(MA)为原料合成马来酸甘油酯(MG),作为多官能度烯类支化单体与丙烯酸(AA)单体,通过自由基共聚法制备水性支化聚合物皮革复鞣填充剂(BPMG)。通过1HNMR对支化单体和聚合物的结构进行了表征。通过正交实验考查了单体配比、引发剂用量、支化单体类型和投料方式对GM双键转化率的影响,结果表明：MG-30为支化单体,n(AA):n(MG)=6:1,w(过硫酸铵)=6%时,以单体滴加的方式,聚合温度85℃,聚合时间2.5 h的条件下,具有较高的双键转化率。应用结果显示支化聚合物可以提供皮革较好的填充性能和力学性能。SEM结果表明支化聚合物对皮革纤维具有明显的分散作用。     

支化聚合物皮革复鞣填充剂的制备及应用

以甘油(Gly)和马来酸酐(MA)为原料合成马来酸甘油酯(MG),作为多官能度烯类支化单体与丙烯酸(AA)单体,通过自由基共聚法制备水性支化聚合物皮革复鞣填充剂(BPMG)。通过1HNMR对支化单体和聚合物的结构进行了表征。通过正交实验考察了单体配比、引发剂用量、支化单体类型和投料方式对MG双键转化率的影响。结果表明,MG-30为支化单体,n(AA)∶n(MG)=6∶1,w(过硫酸铵)=6%时,以单体滴加的方式,聚合温度85℃,聚合时间2.5h的条件下,具有较高的双键转化率。应用结果显示支化聚合物可以提供皮革较好的填充性能和力学性能。SEM结果表明,支化聚合物对皮革纤维具有明显的分散作用。     

高度支化聚合物的应用研究

高度支化聚合物由于其独特的结构和性能使其在世界范围内越来越受到科学家们的关注,是目前发展最快的功能高分子材料之一。针对当今国内外对高度支化聚合物的合成尽应用研究成果进行了简要的综述,并对其以后发展作了展望和预测。     

用二乙烯基苯与丁苯共聚方法研制充油SSBR

在n -BuLi/THF引发体系中 ,采用DVB与丁二烯、苯乙烯共聚方法合成高门尼、多支化的SSBR。考察了共聚单体组分的活性大小、DVB用量及反应时间对聚合物支化度的影响并用该共聚物制备充油SSBR。结果表明Kp″(p -DVB) >Kp″(m -DVB) >Kp″(Bd) >Kp″(St) >Kp″(m -EVB) >Kp″(p -EVB)。DVB用量、反应时间增加 ,聚合物的支化度增大 ,分子量分布加宽。填充不同油品制备的充油SSBR和国内外同类产品相比综合性能优异。用“一步合成法”合成高门尼SSBR ,工艺方法简单 ,门尼粘度及支化度控制较为稳定。     

The architectures and surface behavior of highly branched molecules

This review presents recent developments in the field of the highly branched molecules (excluding dendrimers) with emphasis on their surface behavior, microstructure, surface morphology, and properties. In our consideration, we included popular types of highly branched molecules, such as star molecules with multiple arms, brush macromolecules of different kinds, and hyperbranched molecules, many of them available in relatively large quantities, which is crucial for future applications.     

In vitro degradation behavior of biodegradable 4-star micelles

Drug delivery vectors for sustained release include a variety of polymeric constituents, both natural and synthetic. Among synthetic polymers several linear block copolymer systems have been explored for use as drug delivery vectors. Release of the pharmaceutical agent is affected by the degradation characteristics and/or by the swelling of the polymer. The goal of this study is to evaluate the degradation behavior of branched polyethylene oxide polylactide polyether ester as a drug delivery vector. Three samples of a star polyethylene oxide/polylactide copolymer with differing polylactide chain lengths were evaluated by characterizing the thermal properties of the neat polymer and in vitro degradation behavior.The thermal and morphological properties were examined by DSC, TGA and XRD. The in vitro polymeric micelle samples were observed over time by UV-vis, TEM and fluorescence. The four star PEO-PLA polymers have exceptional amphiphilic characteristics, which enable their use for a variety of applications. The polymers are thermally stable at biological conditions. In addition, the star polymers have shorter degradation times as compared to previously reported linear PLA and PEG-PLA copolymers, suggesting use as a short-term drug release agent. The four star PEO/PLA copolymer may be an excellent candidate for drug delivery applications.     

Preparation of acid-cleavable branched polymers for argon fluoride photoresists via reversible addition–fragmentation chain-transfer polymerization

A series of branched polymers for chemically amplified resists (CARs) were prepared through the reversible addition–fragmentation chain-transfer (RAFT) copolymerization of three monomers with lithographic functionalities and an acid-cleavable dimethacrylate monomer. The three monomers with lithographic functionalities were 2-ethyl-2-adamantyl methacrylate, α-γ-butyrolactone methacrylate, and 3-hydroxy-1-adamantyl methacrylate. The acid-cleavable monomer was 2,5-dimethyl-2,5-hexanediol dimethacrylate (DMHDMA), and 2-cyanoprop-2-yl-1-dithionaphthalate was used as a chain-transfer agent. Because DMHDMA contains two methacrylate groups, it induced the branched structures of the polymers. The degree of branching could be controlled by the molar fraction of DMHDMA in the monomer mixtures. The size and structure of the polymers obtained after hydrolysis were very close to those of linear polymers prepared by RAFT copolymerization with the same amount of reagents, only without the acid-cleavable monomer. A preliminary lithography test using an argon fluoride source demonstrated that the acid-cleavable branched polymers could be promising candidates for CAR materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

超支化聚合物及其自组装研究进展

介绍了超支化聚合物的结构性质特点及合成方法,主要有缩聚反应、乙烯基自缩合反应(SCVP)、开环聚合等;概述了超支化聚合物的自组装及其应用研究情况,如在生物医药、修饰碳纳米管及其它领域的实际应用现状。     

Core-shell polyacrylate and polystyrene-block-polyacrylate stars

The polymerization of p-(iodomethyl)styrene (PIMS) yields well-defined branched polymers with reactive iodomethyl groups. The branched poly[p-(iodomethyl)styrene] was used as the transfer agent in the iodine mediated radical polymerization of vinyl monomers. The polymerization proceeds in a controlled way and yields polystyrene and poly(t-butyl acrylate) star polymers with reactive groups at the end of their arms. Polymers so obtained were also used to prepare stars with block copolymer arms: polystyrene-block-poly(t-butyl acrylate). The characterization of star structures was performed by NMR and gel permeation chromatography with absolute molar mass detection (MALLS). Preliminary characterization of the thermal properties of these novel materials is reported.     

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).     

Self‐condensing atom transfer radical polymerization of inimers of different reactivity ratios with styrene and the thermal properties of poly(2,6‐dimethyl‐1, 4‐phenylene oxide)/branched polystyrene blends

Although the self‐condensing atom transfer radical polymerization (SCATRP) of inimers with typical comonomers has been extensively performed, there have been few reports to correlate the reactivity ratio with the growth of the molecular weights (MWs) and the development of branched structures. Thus, the SCATRP of inimers of different reactivity ratios, namely, 4‐chloromethylstyrene (CMS) and maleimide (MI) inimers, with a large excess of styrene (St) were carried out, respectively, to examine the effect. The conversion and MW were monitored by gas chromatography, gel permeation chromatography, and multiangle laser light scattering. The results suggested that CMS merely functioned as an initiator for St at the early stage; this led to linear macroinimers, which underwent SCATRP and gave rise to randomly branched polystyrene (PS) only at high conversion. The MI inimers formed charge‐transfer complexes with St and underwent the SCATRP to result in hyperbranched copolymers at first; this initiated the atom transfer radical polymerization of St and led to star‐shaped PS. With the objective of improving the processability and melt fluidity, the physical properties of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) blends with linear, randomly branched, and star‐shaped PS were compared. In comparison with those with linear PS, the PPO/branched PS blends exhibited a higher glass‐transition temperature, a higher melt flow index, and a comparable thermal stability because of the spherical architecture of the branched PS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Novel biocidal polymers based on branched and linear poly(hydroxystyrene)

New biocidal polymers based on branched as well as linear poly(p-hydroxystyrene) were synthesized. Biocidal polymers were synthesized in two steps by creation of active centers via chloroacetylation of linear and branched poly(p-hydroxystyrene) using chloroacetyl chloride. The second step involves the immobilization of onium salts onto the chloroacetylated polymers. All the prepared polymers were characterized using elemental microanalysis, FT-IR, ¹H NMR spectra, and TGA. Antimicrobial activity of the prepared polymers was tested against various pathogenic microorganisms. The antimicrobial activity was found to be affected by the active group and the tested microorganism. The phosphonium salts showed higher activity than ammonium salts.     

Branched polysilanes from tetrafunctional monomers

Tetrafunctional silicon monomers have been incorporated into soluble branched polysilanes. Tetrakis(chlorodimethylsilyl)silane has been homopolymerized to form an irregular branched polymer which may contain some spiro and some bicyclic units. This polymer shows weak absorption at 300 nm, the region of the linear polysilane chains. It emits broadly in the region from 400 to 500 nm. The copolymers of tetrakis(chlorodimethylsilyl)silane with dichlorodimethylsilane are also soluble and in the presence of l ge amount of the tetrakis monomer emit in the region from 400 to 500 nm. By contrast, copolymers with phenyltrichlorosilane emit strongly at 450 to 650 nm, due to the phenylsilane hyperbranched structure. Small amounts of tetrachlorosilane can be incorporated into soluble polysilanes. Incorporation of =Si=units into polymers withn-hexyl substituents is very inefficient but leads to minor changes in emission spectra. Incorporation into polymers with phenyl substituents affects luminescence and increases molecular weights and broadens polydispersities. Reaction with dimethyldichlorosilane provides soluble low molecular weight oligomers and polymers. Polymers prepared with a small proportion of tetrachlorosilane show absorption and emission typical for linear polymers. Polymers synthesized with higher proportion of tetrachlorosilanes emit broadly at 400 to 500 nm, indicating the presence of Si clusters. The silicon clusters entrapped into soluble polymers are very easily oxidized as seen by the siloxane peaks in²⁹Si NMR spectra and they should be treated under complete exclusion of oxygen.