Radical polymerization of butyl acrylate and random copolymerization of styrene and butyl acrylate and styrene and methyl methacrylate mediated by monospiro- and dispiropiperidinyl-N-oxyl radicals

Radical polymerization of butyl acrylate (BA) and random copolymerizations of styrene (St) and BA and St and methyl methacrylate (MMA) in the presence of 7-aza-15-hydroxydispiro[5.1.5.3]hexadecane-7-yloxyl (1) and 1-aza-2,2-dimethyl-4-hydroxyspiro[5.6]dodecane-1-yloxyl (2) were carried out. Radical polymerization of BA at 120 °C in the presence of 1 gave poly(BA) with M_n=20200 and M_w/M_n=1.30 at 23% conversion. The termination of polymerization observed around ∼20% conversion was solved to a certain extent by an addition of small amounts of dicumyl peroxide, and poly(BA) with M_n=37400 and M_w/M_n=1.33 was obtained in 46% yield. Random copolymerizations of St and BA and St and MMA in the presence of 1 and 2 at 80 °C gave the corresponding random copolymers with narrow polydispersities of 1.12-1.38 at the molar fraction above 0.30 of St in feed. The kinetic study for the NO-C bond homolysis of the corresponding alkoxyamines prepared from 1 and 2 were carried out, and evaluation of the preexponential factors (A_act) and the activation parameters (E_act) showed that the steric factors of the nitroxides are reflected mainly on E_act.     

Physical and electroresponsive characteristics of the intercalated styrene‐acrylonitrile copolymer/clay nanocomposite under applied electric fields

Styrene‐acrylonitrile copolymer (SAN)/clay nanocomposites were synthesized through an emulsion copolymerization of styrene and acrylonitrile in the presence of sodium montmorillonite, and their physical properties and electroresponsiveness under an applied electric field were characterized. Thermogravimetric analysis (TGA) showed that the thermal stability of the synthesized polymer was sustained. X‐ray diffraction (XRD) analysis confirmed the insertion of SAN into the interlayers of clay, whose separation consequently increased, as compared to those of the pristine clay. Transmission electron microscopy (TEM) was used to observe the suspended state of clay. Dry‐base electrorheological (ER) fluids were prepared by mixing intercalated SAN nanocomposite particles into silicone oil. Typical ER behavior, i.e., enhancement of shear and yield stresses in the presence of an applied electric field, was observed using a rotational rheometer equipped with a high‐voltage generator. A universal yield stress scaling equation was also found to fit our experimental data well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 821–827, 2003     

Preparation of iodine containing quaternary amine methacrylate copolymers and their contact killing antimicrobial properties

A novel quaternary amine methacrylate monomer (QAMA) was synthesized by amination of dimethacrylate with piperazine followed by its quaternization using an alkyl iodide. Copolymerization of QAMA with 2‐hydroxyethyl methacrylate was carried out by free radical bulk polymerization technique at room temperature using ammonium persulfate and N,N,N′,N′‐tetramethyl ethylenediamine as a redox initiator. The monomer as well as copolymers was characterized by FTIR and ¹H NMR spectral studies. Thermal and physical characteristics of copolymers of varying compositions of QAMA were evaluated by thermogravimetric analysis, differential calorimetry, contact angle and scanning electron microscopy. The antibacterial activity of the synthesized quaternary amine dimethacrylate copolymers against Escherichia coli and Staphylococcus aureus was studied by zone of inhibition and colony count method. QAMA copolymers showed broad‐spectrum contact killing antibacterial properties without releasing any active agent as checked by iodide‐selective ion meter. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1038–1044, 2006     

聚合度对纤维素表面性能的影响

根据Washburn浸渍理论和van Oss-Good-Chaudhury组合理论及应用柱状灯芯技术测试了具有不同聚合度(DP)的纤维素的表面性能,同时与已报道的纤维素的表面能进行了比较。结果表明:纤维素的表面能随分子量的增加而增大,但主要是其Lifshitz-van der Waals力在起主导作用。研究还发现纤维素的表面能γS与聚合度DP之间的关系大致可以描述为:γS=37.56+0.02 DP,而纤维素的极性率P与聚合度DP之间的关系则是一种非线性关系,如:P=11.88-0.02 DP+9.10 DP2。     

具有硬核—软壳结构的丙烯酸聚合物乳液的研究

利用种子乳液聚合法合成了具有硬核—软壳结构的丙烯酸聚合物微粒子,通过对种子粒子数和最终粒子数的理论计算,并结合最低成膜温度(MFT)的测试结果,描述了聚合物微粒子的聚合过程,同时,还对聚合物乳液的各项性能进行了研究。     

分批加分散剂时苯乙烯悬浮聚合瞬间液滴直径和分布

在苯乙烯悬浮聚合中研究了分批加分散剂体系磷酸三钙(TCP)或 TCP 和聚乙烯醇(PVA)时的加入方式对瞬间液滴大小和分布的影响。考察了体系液滴分散和合一的特点。实验观察到分批加入分散剂体系时液滴大小分布的变化规律,呈由单峰分布过渡到双峰分布,最后又发展为单峰分布。这与分散剂体系一次加入相比,后者仅出现单峰分布逐渐过渡到双峰分布。     

分散聚合及单分散聚合物微球制备技术

分散聚合是一种新的聚合方法 ,反应开始前 ,单体、引发剂和分散剂均溶解在介质中 ,随着反应的进行 ,当聚合物链达到临界值时便会从介质中分离出来 ,并借助于分散剂稳定地悬浮在介质中。分散聚合方法已被应用于许多领域 ,如涂料工业、生物工程、医学、信息产业、化学工业等。介绍了分散聚合及单分散聚合物微球制备技术的进展 ,并对其聚合机理及聚合反应影响因素进行了概述。     

Ceramic Microtubes from Preceramic Polymers

A novel process for the production of ceramic microtubes involving the microextrusion of preceramic polymers was studied. Microtubes with a wide range of inner and outer diameters and several centimeters long were produced from two silicone resins. A coextrusion approach was also used to extend the forming capability of the technique. The addition of carbon black resulted in electrically conductive silicon oxycarbide (SiOC) ceramic microtubes. SiOC microtubes possessed a high bending strength, ranging from ∼30–1100 MPa.     

聚吡咯／尼龙6复合导电纤维的研制

采用原位聚合法,在吡咯的水性溶液中可制备具有良好导电性的聚毗咯／尼龙6复合纤维。文章探讨了反应过程中各种因素对所制得的聚吡咯／尼龙6复合导电纤维导电性的影响。结果表明,FeCl3是一种较为有效的氧化剂。采用吡咯单体浓度为0．05 mol/L、氧化剂与吡咯的初始摩尔比为2．3、反应温度为20℃,反应时间为3 h的反应条件,可制得具有较好导电性的复合纤维。电镜照片显示,复合导电纤维呈现皮芯结构,聚吡咯主要集中在皮层,形成导电通道。     

An Application of Silica‐Based Monolithic Membrane Emulsification Technique for Easy and Efficient Preparation of Uniformly Sized Polymer Particles

Summary: Uniformly sized polymer particles were prepared by an emulsification and polymerization technique utilizing a silica monolithic membrane, namely the “silica monolithic membrane emulsification technique”. In this paper, we utilized silica monolithic membrane as a device for the preparation of uniformly sized polymer particles. A mixture of monomers, diluents and oil‐soluble initiator was emulsified into a continuous medium through the silica monolithic membrane and polymerized. The particles obtained had a higher size uniformity than that of particles prepared by previously reported membrane emulsification techniques, such as the Shirasu Porous Glass (SPG) emulsification technique. Through the silica monolithic membrane emulsification technique, we could prepare particles having availability as a possible packing material for solid‐phase extraction (SPE) and high performance liquid chromatography (HPLC).

SEM photograph of silica particles prepared through capillary plate membrane.