共查询到20条相似文献,搜索用时 15 毫秒
1.
Based on an improved calculation of activity coefficients, continuous thermodynamics using a generalized divariate Stockmayer distribution is applied to the liquid-liquid equilibrium of random copolymer solutions. The effects of the chemical polydispersity on the cloud-point curve, the shadow curve, the spinodal, and the critical point are discussed. The theory can account for the occurrence of three-phase equilibria as well as for the phase separation in pure copolymers. 相似文献
2.
ABSTRACT A solution of a random copolymer showing polydispersity only with respect to chemical composition is considered. A model distribution very flexible in its breadth and in its asymmetry is used to describe the polydispersity. Based on continuous thermodynamics, equations for the cloud-point curve, the shadow curve, the spinodal, the critical point, and the heterogeneous double critical point are derived. the activity coefficients are calculated with the aid of Huggins' χ-parameter concept assuming χ to depend linearly on the average chemical composition of the copolymer. the influence of the breadth and the asymmetry of the distribution on the liquid-liquid equilibrium of the copolymer solution is discussed. 相似文献
3.
The sequence distributions for the copolymers generated in three cases of binary equilibrium copolymerization, including the effect of the ultimate unit, are studied theoretically. From the equilibrium sequence distribution functions, the copolymer sequence structure, the number- and weight-average sequence lengths of monomer units, the run number, the randomness parameter, and the fractions of different diads in the copolymer are derived. According to the relation between the parametric variables introduced in the formulas and the equilibrium copolymerization conditions, all of the structural sequence parameters of the resulting copolymers can be predicted from the comonomer feed composition and the equilibrium constants for initiation and propagation. Finally, the relation between the reaction temperature and the structural sequence parameters is given. 相似文献
4.
5.
6.
In this paper, a unique and updated technique was applied to obtain an acid dyeable copolymer of acrylonitrile by solution polymerization of acrylonitrile, and a kind of alkaline monomer F (N,N‐dialkylaminoethylacrylate). Azodiisobutyronitrile (AIBN) was used as initiator to prepare the copolymer in sodium sulfocyanate aqueous solution. The effect of initiator concentration on the polymer's molecular weight and conversion during polymerization was studied. The relation between concentration of the alkaline monomer F and the polymer conversion, as well as the relation between concentration of the alkaline monomer F and the % dye‐uptake of the copolymer are discussed. The influence of pH was also researched. The structure of the copolymer was characterized by IR and NMR. The copolymer has excellent acid dyeable characteristics. 相似文献
7.
在四氢呋喃(THF)与环己烷的混合溶剂中,以正丁基锂(n-BuLi)为引发剂,采用具有较大空间位阻和特定电荷环境的P配合物为添加剂,实现了异戊二烯(Ip)和甲基丙烯酸甲酯(MMA)的阴离子嵌段共聚。分别采用GPC、^1H—NMR对聚合物的结构进行了分析表征。结果表明:随着THF与环己烷体积比的增大,单体的转化率呈现下降的趋势;同时空间位阻较大的P配合物的加入,堵塞了正、负离子对之间的部分通道,有效地抑制了MMA段聚合副反应的发生,在易于工业化的0℃之下成功合成了分子量分布窄(1.21)的聚异戊二烯一聚甲基丙烯酸甲酯嵌段共聚物(PI—b—PMMA),并且共聚物中PI嵌段以3,4结构链节为主。 相似文献
8.
9.
Continuous thermodynamics was developed in recent years and applied successfully to the liquid-liquid equilibrium of poly disperse polymer solutions. Continuous thermodynamics is based on the direct use of continuous distribution functions in the thermodynamic equations. There is no need for a reduction to pseudocomponents. This paper presents the application of continuous thermodynamics to successive polymer fractionation procedures based on solubility differences. In this way, simple equations for the distribution function of the different polymer fractions are obtained. Furthermore, the other equations describing the fractionation possess a lucid structure favorable for computer simulations of the fractionation procedures. 相似文献
10.
Michael Szwarc 《Journal of polymer science. Part A, Polymer chemistry》1998,36(2):v-xiii
The principle of the electron photoejection technique is explained. This approach leads to the formation of transient spectra of unstable intermediates, allowing their recording and providing their extinction coefficients. Moreover, it permits determination of their electron affinities and the rates of their reactions, whether spontaneous or with some added substrates. Application of this technique to studies of disproportionation of radical anions has been most profitable. It led to the determination of the forward and backward rate constants of disproportionation of a variety of radical anions, and to discovery and quantification of some subtle features of these reactions. The electron photoejection technique provided the data characterizing the electron transfer initiation of anionic polymerization and clarified some of its features. Other opportunities provided by the electron photoejection in studies of electron transfer processes are suggested. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: v–xiii, 1998 相似文献
11.
12.
13.
We present a combinatorial approach to the synthesis of block copolymer series by anionic polymerization, utilizing a specially designed reactor setup. The setup features one main reactor and three secondary reactors to carry out anionic polymerizations on laboratory‐scale quantities at low temperatures. The implementation was demonstrated with three series of AB‐ and ABC‐block copolymers with identical A‐ and AB‐blocks, respectively. The B‐block in AB‐diblock copolymers and the C‐block in ABC‐triblock copolymers can be varied with respect to block length or chemical constitution. Well‐defined series of block copolymers are useful for advanced optimization of functional block copolymers in nanotechnology applications.
14.
Masayoshi Tanaka Atsushi Sudo Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):4417-4423
A solid‐supported samarium enolate successfully initiated the polymerization of 2‐(trimethylsilyloxy)ethyl methacrylate (TMS‐HEMA) through the living anionic process. In addition, the silyl group was readily removed by treatment of the beads with a weak acid to afford the corresponding well‐defined poly(methacrylate) having a hydroxyethyl group in the side chain (PHEMA). The hydroxyl group of the immobilized PHEMA on the beads was successfully acetylated to give poly(2‐acetoxyethyl methacrylate), which could be quantitatively isolated from the beads by trifluoroacetic acid treatment. Moreover, the hydroxyl group of the immobilized PHEMA could be utilized as an initiator for acid promoted ring opening polymerization of lactone to yield the corresponding graft copolymer. In this method, the residual and excess reagents could be removed by filtration, which demonstrated the applicability of the present technique to a novel method for construction of functional polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4417–4423, 2004 相似文献
15.
通过甲基丙烯酸N,N-二甲氨基乙酯(dimethylamino ethyl methacrylate)和环己内酯(ε-caprolactone)之间的连续阴离子聚合, 合成了末端含有氨基的聚甲基丙烯酸N,N-二甲氨基乙酯-嵌段-聚己内酯的双亲性嵌段共聚物(PDMAEMA-b-PCL). 为了增强生物相容性, 通过末端氨基与D-葡萄糖酸内酯(D-gluconolactone)的酰胺化反应对该共聚物进行糖基修饰. 合成的共聚物的化学结构用氢核磁共振光谱(1H NMR)和红外光谱(IR)进行表征, 聚合物的分子量分布采用凝胶色谱(GPC)测定, 该嵌段共聚物在水溶液中的自组装行为则借助于动态光散射(DLS)进行了研究. 相似文献
16.
Joonkeun Min Priyank N. Shah Chang‐Geun Chae Jae‐Suk Lee 《Macromolecular rapid communications》2012,33(23):2029-2034
Poly(furfuryl isocyanate) (PFIC), which includes the reactive furan group, was synthesized by anionic polymerization using a sodium benzhydroxide (Na‐BH), self‐assembly initiator. We determined the optimum polymerization conditions by varying both the reaction time and the molar ratio of the monomer to the initiator. Block copolymer, poly(furfuryl isocyanate)‐b‐poly(n‐hexyl isocyanate), was synthesized under optimized polymerization conditions. The PFIC was modified by Diels–Alder reactions with C60 for functionalization. Transmission electron microscopy (TEM) was used to study the self‐assembly of block copolymers and modified block copolymer with C60. C60 formed highly ordered aggregates on the PFIC domains via self‐assembly of the block copolymer. 相似文献
17.
This work confirms the new view of the initiation and propagation mechanism of the anionic polymerization previously proposed, based on the investigation of anionic bulk‐polymerization of styrene and α‐methyl styrene with the help of a self designed microflow device and characterized by GPC and in situ 7Li NMR. It was found that n‐BuLi tended to form the hexameric‐aggregated structure and even to form the huge aggregated structure based on the former. These aggregations of initiators could directly initiate the anionic polymerization and form the supramolecule aggregations. The supramolecule aggregations inevitably blocked the diffusion of the monomers to the ion‐pairs and resulted in a stationary‐conversion platform. Then the aggregators were dissociated completely into equal binary‐aggregated species, and the polymerization continued again rapidly before the termination. Tetrahydrofuran (THF) acted as the electron donator, which could push the electron cloud to Li cation and make the aggregated ring of the active species rather loosened and facilitated the monomer to insert in. Therefore, a little THF can greatly promote the anionic polymerization. However, further addition of THF might block the channel between the ion‐pairs and decrease the propagation rate. It was also found that the aggregated structure of the active species during the anionic polymerization only depends on the initiator aggregations which were formed before the polymerization. 相似文献
18.
Roderic P. Quirk Tae-Hee Cheong Kevin Jiang Deanna L. Gomochak Taejun Yoo Keith T. Andes Robert T. Mathers 《Macromolecular Symposia》2003,195(1):69-74
Recent results for the preparation of chain-end functionalized polymers using alkyllithium-initiated anionic polymerization are described. Termination with 4-chloro-1,1,1-trimethoxybutane has been used to prepare trimethoxy ortho ester (carboxyl)-functionalized polymers. Functionalization with the oxiranes, glycidoxypropyltrimethoxysilane, 3,4-epoxy-1-butene and 1,1,1-trifluoro-2,3-epoxypropane, has been investigated to prepare trimethoxysilyl-functionalized polymers, 1,3-diene-functionalized macro monomers and trifluoromethyl-functionalized polymers, respectively. Secondary amine-functionalized polymers have been prepared by termination with N-(benzylidene)methylamine and also using an N-benzyl tertiary amine-functionalized alkyllithium initiator followed by hydrogenolysis of the benzyl group. 相似文献
19.
Lian R. Hutchings Jonathon M. Dodds Susan J. Roberts-Bleming 《Macromolecular Symposia》2006,240(1):56-67
We describe here a new strategy for the synthesis of polymers with highly branched architectures. The strategy involves the synthesis by anionic polymerization of well-defined AB2 polystyrene macromonomers with molecular weights from 3,600 to 94,000 gmol−1, which are then converted via a one-pot polycondensation reaction into high molecular weight, long-chain (hyper)branched architectures. Since the Hyperbranched structures are built up from condensation Macromonomers we have coined the term ‘HyperMac’ to describe these branched polymers. In this paper we report the synthesis of the HyperMacs, the optimal conditions for the polycondensation reaction and some preliminary characterization studies. 相似文献