The mechanism of the oxidative polymerization of aniline and the formation of supramolecular polyaniline structures

Polyaniline is one of the most important conducting and responsive polymers. A molecular mechanism for the oxidation of aniline is proposed. This mechanism explains the specific features of aniline oligomerization and polymerization in various acidity ranges. The formation of polyaniline precipitates, colloids and thin films is reviewed and discussed on the basis of the chemistry of aniline oxidation. The generation of nanostructures, i.e. granules, nanotubes, nanowires and microspheres, is also considered. Oligomers containing phenazine constitutional units play an important role in self‐assembly to form templates. Polyaniline chains then grow from these templates and produce the various individual morphologies. Copyright © 2008 Society of Chemical Industry     

Reversible addition–fragmentation chain transfer polymerization of styrene using a novel thiophene dithioester as the reversible addition–fragmentation chain transfer agent

Benzyl thiophene‐2‐carbodithioate and 2‐methyl‐2‐(4‐methylcyclohex‐3‐enyl)propyl thiophene‐2‐carbodithioatewere synthesized. The reversible addition–fragmentation chain transfer polymerizations of styrene with benzyl thiophene‐2‐carbodithioate and 2‐methyl‐2‐(4‐methylcyclohex‐3‐enyl)propyl thiophene‐2‐carbodithioate as chain‐transfer agents and with 2,2′‐azobisisobutyronitrile as an initiator were carried out. The polymerization kinetics were investigated. An ab initio calculation method was used to explore the differences between benzyl thiophene‐2‐carbodithioate and benzyl benzodithioate. The structure of the obtained polymers was characterized with ¹H‐NMR. Chain‐extension experiments of the obtained polymer with styrene were carried out. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

间规1,2—聚丁二烯合成的实验室研究

报道了使用Ｃｏ－Ａｌ－Ｐ－Ｈ２Ｏ催化体系实验室合成间规１，２－取丁二烯的研究结果，详细讨论了催化组分的加料顺序，老化条件及聚合工艺条件对聚合反应的影响，在此基础上得到最佳工艺条件，进行了模试放大，所得聚合物的基本性能与ＪＳＲ ＲＢ８２０相近。     

Emulsion polymerization: State of the art in kinetics and mechanisms

Over decades of carefully designed kinetic experiments and the development of complementary theory, a more or less complete picture of the mechanisms that govern emulsion polymerization systems has been established. This required means of determining the rate coefficients for the individual processes as functions of controllable variables such as initiator concentration and particle size, means of interpreting the data with a minimum of model-based assumptions, and the need to perform experiments that had the potential to actually refute a given mechanistic hypothesis. Significant advances have been made within the area of understanding interfacial processes such as radical entry and exit into and out of an emulsion polymerization particle, for electrostatic, steric and electrosteric stabilizers (the latter two being poorly understood until recently). The mechanism for radical exit is chain transfer to monomer within the particle interior to form a monomeric radical which can either diffuse into the water phase or propagate to form a more hydrophobic species which cannot exit. Entry is through aqueous-phase propagation of a radical derived directly from initiator, until a critical degree of polymerization z is reached; the value of z is such that the z-meric species is sufficiently surface active so that its only fate is to enter, whereas smaller aqueous-phase radical species can either be terminated in the aqueous phase or undergo further propagation. For both entry and exit, in the presence of (electro)steric stabilizers, two additional events are significant: transfer involving a labile hydrogen atom within the stabilizing layer to form a mid-chain radical which is slow to propagate and quick to terminate, and which may also undergo β-scission to form a water-soluble species. Proper consideration of the fates of the various aqueous-phase radicals is essential for understanding the overall kinetic behaviour. Intra-particle termination is explained in terms of diffusion-controlled chain-length-dependent events. A knowledge of the events controlling entry and exit, including the recent discoveries of the additional mechanisms operating with (electro)steric stabilizers, provides an extension to the micellar and homogeneous nucleation models which enables particle number to be predicted with acceptable reliability, and also quantifies the amount of secondary nucleation occurring during seeded growth. This knowledge provides tools to understand the kinetics of emulsion polymerization, in both conventional and controlled/living polymerization systems, and to optimize reaction conditions to synthesize better polymer products.     

Synthesis and characterization of grafted copolymers of aromatic polyimides and ε‐caprolactam

Anionic polymerization of ε‐caprolactam was performed in the presence of only 5 wt % of aromatic polyimides having five‐ and six‐membered imide cycles and bearing hexafluoroisopropylidene, ether, fluorene, siloxane, phthalide, or SO₃H? groups, both in the polymer backbone and as side moieties. The synthesized new copolymers were fully characterized by IR spectroscopy, thermomechanical analysis, dilatometry, and X‐ray diffraction. Tough and frictional properties of the obtained copolymers were estimated as well. It was found that on the selection of polyimide activator it is possible to gain the desirable control over the polymer properties, namely the gel‐fraction content, phase composition, compression modulus, notched Izod impact strength, temperature of frictional contact, friction coefficient, etc. These investigations will facilitate the choice of the optimum macromolecular activator for the modification of both the synthetic method and the properties of the commercial polycaproamide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

双功能改性丙烯酸树脂皮革涂饰剂的研制

在丙烯酸丁酯—丙烯腈—丙烯酸甲酯体系中，引入１％～２％的丙烯酸，２％～３％的Ｎ－羟甲基丙烯酰胺，５％的烷基酚聚氧乙烯醚硫酸铵与十二烷基硫酸钠复配乳化剂，采取自生种子聚合技术可制得双功能团改性的丙烯酸树脂皮革涂饰剂。     

Design of multi-layer coated particles with sigmoidal release pattern

In order to design and control the release pattern of an active solid component, we investigated the release characteristics of core particles coated with multiple layers of fine permeable particles surrounding soluble particles dispersed in layers of impermeable wax. We examined the effect of operational conditions on the parameters of the release profile by multivariate analysis, and obtained simplified correlations for the maximum release rate and the lag time of the release curve as a function of the volume fraction of permeable particles and the thickness of the permeable- and soluble-particle layers. The results confirmed that the desired release rate could be obtained in the first place by adjusting the volume fraction and the thickness of the permeable-particle layer, while it was also possible to attain the required lag time by changing the thickness of the soluble layer. Finally, the calculation examples successfully illustrated the possibility of our being able to design the controlled-release particles with a prescribed sigmoidal release.     

A Convenient Method for Preparation of Amphiphilic Monomethoxypoly (Ethylene Glycol)–Polystyrene Diblock Copolymer by NMRP Technique

Amphiphilic block copolymers are macromolecular compounds of great importance from both fundamental scientific and many technological point of views for a large variety of applications. Amphiphilic diblock copolymer containing segments of monomethoxypoly(ethylene glycol) and polystyrene (MPEG-b-PS) was synthesised by a convenient method for preparation of macroinitiator MPEG-TEMPO for ‘living’ free radical polymerization (NMRP technique). Initially, derivative of MPEG with chlorine function has been prepared in an one-step reaction with thionyl chloride. 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-OH) obtained by reduction of 2,2,6,6-tetramethyl-piperidinyl-1-oxy (TEMPO) with sodium ascorbate was coupled with chlorinated MPEG to yield the macroinitiator MPEG terminated with a TEMPO unit (MPEG-TEMPO), which was further used to prepare the diblock copolymer MPEG-b-PS of styrene. The product was purified and identified by ¹H NMR, GPC and, FT-IR.