摘要:

AbstractEt(ind)2ZrCl2(C2H5(indenyl)2ZrCl2) confined inside regular pores of molecular sieves MCM‐41 and VPI‐5 were prepared and used to polymerize propene with high activity. Stereoregularity, melting point and molecular weight of polypropene obtained were increased and the polymerization behavior was quite different from that prepared with homogeneous Et(ind)2ZrCl2. The small, regular and cylindrical pores of MCM‐41 and VPI‐5 suppress the formation of inactive binuclear complexes between metallocene and metallocene, or between metallocene and methylaluminoxane, resulting in stable active sites and high activity in propene polymer

ISSN:1022-1336    

DOI:10.1002/marc.1996.030171101

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA novel photo‐driven liquid crystal (LC) cell was fabricated by sandwiching nematic LC molecules between two quartz plates whose surface was modified with 4‐hexyloxy‐4′‐undecanyloxyazobenzene (6Az11)‐grafted ladderlike copoly(methylhydrosilsesquioxane) (PMHSQ). Reversible changes of the alignment between homeotropic and planar modes were achieved. The transmittance through the cell and crossed polarizers could be controlled by the irradiation intensity of 365 nm UV light. A high contrast ratio over 100:1 w

ISSN:1022-1336    

DOI:10.1002/marc.1996.030171102

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractFerroelectricity and thus piezoelectricity are well known features of low molar mass chiral smectic C (Sc*) liquid crystals. We present a new technique to orientate macroscopically the director as well as the smectic layers of a Sc*‐polymer network by applying a suitable mechanical field. The uniform orientation of the network film is checked by X‐ray diffraction. According to the phase symmetry electromechanical measurements indicate the existence of a polar axis of the network and the direct as well as the inverse piezoelectric effect is demonstra

ISSN:1022-1336    

DOI:10.1002/marc.1996.030171103

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractStyrene/ethyl methacrylate (SEMA) colloids were obtained by cocondensation at 77 K of the monomers with several metals such as Au, Pd, In and Sn. The colloids were polymerized with 2,2′‐azoisobutyronitrile and dibenzoyl peroxide as radical initiators at 60°C for 3.5 h. A viscosity average molecular weight (104

ISSN:1022-1336    

DOI:10.1002/marc.1996.030171104

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

Abstract1,3‐Butadiene, 4‐methyl‐1,3‐pentadiene and styrene were polymerized with dicyclopentadienyltitanium dichloride/methylaluminoxane (Cp2TiCl2/MAO) and dicyclopentadienyltitanium chloride/MAO (Cp2TiCl/MAO). These systems are less active than cyclopentadienyltitanium trichloride/MAO (CpTiCl3/MAO), but show the same stereospecificity as the latter; they give predominantly cis‐1,4‐polybutadiene, 1,2‐syndiotactic poly(4‐methyl‐1,3‐pentadiene) and syndiotactic polystyrene. Cp2TiCl/MAO is much more active than Cp2TiCl2/MAO; this is probably due to the fact that in the reaction of Cp2TiCl2with MAO, only a small amount of Ti(IV) is reduced to Ti(III), which is the active species in the polymerization of styrene and 1,3‐dienes. An interpretation of the structure of the active species in Cp

ISSN:1022-1336    

DOI:10.1002/marc.1996.030171105

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractPotassium hydride with 1,4,7,10,13,16‐hexaoxacyclooctadecane (18‐crown‐6) was used in the anionic polymerization of (butoxymethyl)oxirane. Polymers with low ratio of mass‐ to number‐average molar masses (M̄w/M̄n<1.1) were obtained, each macromolecule being terminated (after hydrolysis) with a hydroxyl group on both of its ends. Chain transfer reactions to the monomer were not observed to operate in

ISSN:1022-1336    

DOI:10.1002/marc.1996.030171106

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe design and synthesis of a new unsymmetric monomer, 1‐chloro‐4‐(4‐fluorobenzenesulfonyl)naphthalene (1), was accomplished and polymerized with several bisphenols. Three of these polymers represent the successful incorporation of a bulky 1,4‐naphthylene unit into the commercially known polysulfones, Udel, Radel R and Victrex. All unsymmetric polysulfones obtained were determined to be amorphous and displayed glass transition temperatures in the range of 218–288°C. The gas permeability suffered while the permselectivity was marginally improved with naphthyl inserti

ISSN:1022-1336    

DOI:10.1002/marc.1996.030171107

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThermal reactions of alkali salts of 4‐(1‐bromoethyl)benzoic acid in bulk were investigated. These reactions were found to produce unexpectedly the graft copolymer, poly(4‐vinylbenzoate)‐graft‐oligo(oxycarbonyl‐1,4‐phenylenethylidene) (1). The relative reactivity of the oligocondensation as well as the vinyl polymerization of the salts decreased in the following order: K>Na>Li. The reaction polymerization rate proceeded rapidly during the initial 15 min, and the

ISSN:1022-1336    

DOI:10.1002/marc.1996.030171108

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA series of smectic C*liquid‐crystalline (LC) block copolymers were successfully synthesized via the living anionic polymerization of polystyrene with optically active methacrylate monomers containing (S)‐2‐methylbutyl 4‐(4‐hydroxyphenylcarbonyloxy)‐biphenyl‐4′‐carboxylate mesogens. These materials are the first reported smectic C*block copolymers. Anionic polymerization in tetrahydrofuran (THF) at −70°C leads to LC block molecular weights of approximately twenty repeating units. The number‐average molecular weight of the polystyrene block was varied from 7000 to 20000 to adjust the composition in the block copolymers. Differential scanning calorimetry and optical microscopy indicate that the smectic C*phase is present in the systems over br

ISSN:1022-1336    

DOI:10.1002/marc.1996.030171109

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractStyrene and the cationic surfactant 11‐(acryloyloxy)undecyl(trimethyl)ammonium bromide (AUTMAB) form transparent, globular microemulsions in water without any addition of a cosurfactant. Upon γ‐irradiation, the two monomers copolymerize at room temperature and form nanolatex particles of about 21 nm in diameter consisting of a copolymer with a mole ratio of styrene to surfactant of approximately 1.5:1. Excess surfactant is polymerized in the micellar solution by formation of homopolymer. A structure model is presented taking into account that the surfactant most likely forms the particle shell. Due to the polar, covalently bonded shell the polymer particles can be easily redispe

ISSN:1022-1336    

DOI:10.1002/marc.1996.030171110

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY