摘要:

AbstractThe model of Maxwell et al. (Macromolecules24, 1629 (1991)) for initiator efficiencies in emulsion polymerization has been extended to take into account the effect of added chain transfer agent (CTA). The model supposes that the rate‐determining step for radical entry into latex particles is aqueous‐phase propagation of the primary free radicals to a critical chain lengthzrequired for entry (forming species such as.MzSO −4, where M is a monomer entity and peroxodisulfate S2O 2−8is the initiator). The effect of CTA on the entry rate is assumed to occur by facilitating the production of aqueous‐phase free‐radical species (CTA.) by transfer between species such as.MzSO −4(wheren

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930201

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe reaction of naphthylacetic acid (a plant growth stimulator) on epoxidized 1,4‐polyisoprene has been studied. The increase of the rate of addition of the acid on the oxirane rings, catalyzed by the tetramethylammonium salt of the acid, with temperature, time and concentration of the reagents, is fairly well represented by a second‐order kinetic

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930202

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe enzymatically catalyzed acylation of poly[N‐(2‐hydroxypropyl)‐11‐methacryloylaminoundecanamide‐co‐styrene] and the corresponding monomer was performed in the presence of a lipase, with vinyl acetate, phenyl acetate, 4‐fluorophenyl acetate and phenyl stearate as acylating agents. The kinetics of the enzymatically catalyzed reaction was followed by1H NMR spectroscopy and correlated with sterical and chemical effects. The reactivity of monomer towards acylation is higher than that of the copolymer, and that of the copolymer depends on copolymer composition, pointing at steric and hydrop

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930203

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper reports on the synthesis and characterization of graft copolymers built up by amorphous poly(methyl methacrylate) grafts and a side‐chain liquid‐crystalline backbone. The interest was focussed on the copolymerization behaviour of the liquid‐crystalline monomers and styryl‐terminated methyl methacrylate macromonomers. The radical polymerization of the liquid‐crystalline monomers depends on the liquid‐crystalline monomer concentration and on the amount and length of the grafts (macromonomers). The liquid‐crystalline backbone is the longer the higher the concentration of the mesogenic monomers itself and the smaller the molecular weight of the macromonomers. Variation of the amounts of grafts yielded a maximum length of the liquid‐crystalline backbone at approximately 4 mol‐% (for a molecular weight of 7

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930204

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

Abstracttrans‐1,2‐Di(2‐furyl)ethylene (2) was oxidized with several inorganic oxidants such as FeCl3,CuCl2and Na2S2O8under varying conditions to give a “doped” polymer in a one‐step reaction. Such polymeric salts show typical semiconductor properties, and the electrical conductivity increases with increasing degree of oxidized units in the polymeric structure. The influence of the oxidizing agent and the conditions of the reaction on the composition and the electrical conductivity were studied. The black polymer, which was synthesized by oxidation with FeCl3in a mole ratio monomer/oxidizing agent of 1 to 6 in acetonitrile for 16 h at 20°C, shows the highest electrical conductivity of 2,0 ·

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930205

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractFor random copolymerization of ethylene and propene, the catalytic activity was studied of various catalyst systems consisting of TiCl3prepared by reduction of TiCl4with hydrogen. The extent of reduction of TiCl4markedly affects the activity of the catalyst. Furthermore, the combination of solvent and donor affects the activity, and 1,2‐dichloroethane and dibutyl ether (DBE) was found to be the most favourable combination. Metal halides (MXn) such as VCl4and VOCl3enhance the activity of the TiCl3catalyst. Concerning the co‐catalyst, triisobutylaluminium results in the highest activity. As a whole, both the catalytic activity of these catalyst systems and the structure of the resulting copolymer are largely dependent on the solubility of the catalyst system. The copolymer obtained with a soluble TiCl3· DBE · Al(isobutyl)3system is highly isotactic in the PPP triad and has a lower content of inversion than a copolymer prepared with a conventional VOCl3catalyst system. Moreover, the copolymer obtained with the above TiCl3catalyst has superior physical properties, especially tensile properties, in comparison with the copolymer obtained with the conventional

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930206

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractNew mono‐ and bifunctional isopropenyl derivatives ofo‐carborane were synthesized according to the Witting reaction, from the corresponding acetyl derivatives and methylenetriphenylphosphorane. The radical copolymerization with methyl methacrylate was investigated and thermal and thermomechanical characteristics of the obtained copolymers were studied. In copolymers prepared on the basis of a monofunctional carborane‐containing monomer, the increase of glass transition temperature takes practically a linear course with increasing boron content. In crosslinked copolymers the presence ofo‐carborane fragments leads to the widening of the glass transition temperature range, predominantly at low temperatures, irrespective of the type of bifunctional monom

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930207

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe homopolymerizations of methyl methacrylate (MMA) inN‐methyl‐2‐pyrrolidone (NMP) and ofN‐vinyl‐2‐pyrrolidone (NVP) in methyl isobutyrate (MiB) were investigated at 60°C using AIBN as initiator. Reaction rate and dynamic viscosity of the medium were determined as function of monomer dilution. It follows from the estimated monomer exponentnthat MMA reacts in NMP faster (n= 0,739) and NVP in MiB slower (n= 1,495) in comparison with reaction rates obtained from the direct proportionality of monomer concentration. The observed deviation was quantitatively separated in partial deviations caused by chain initiation, propagation and termination. It was found that the viscosity effect on chain termination plays a dominant role in the global solvent effect. Chain propagation is influenced by electron donor‐acceptor interactions between monome

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930208

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractThe aromatic thionoester3(benzyl thionobenzoate) was an effective chain transfer agent in polymerizations of styrene (Cx= 1,0) and methyl acrylate (Cx= 1,2) at 60°C. This activity was close to the ideal for obtaining narrow molecular‐weight distributions in batch polymerizations. The thionoester3showed no activity in polymerizations of methyl methacrylate, but was too reactive to be useful in vinyl acetate polymerizations. Ring‐substituted thionoesters9‐11and14and1H NMR spectroscopy of the resulting polymers were used to establish the type and quantity of end‐groups. The thionoester12was used to produce low‐molecular‐weight polystyrene that was terminated at one end with a hydroxy group and at the other end by a thiolo

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930209

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY

摘要:

AbstractPoly[bis(p‐phenylphenoxy)phosphazene] (PB(4‐Ph)PP) has been investigated employing X‐ray diffraction technique and electron microscopy. Its unit cell dimensions were determined to bea= 4,18 nm,b= 1,83 nm andc= 0,957 nm with space group Pca21. At 21 5–220°C , PB(4‐Ph)PP transforms into an anisotropic liquid‐like phase corresponding to a new molecular ordering array. The thicker films are composed of the linked globules approximately 100 nm in diameter. Upon drawing, the globules transform into a rod‐like morphology 15–40 nm in width and exhibit a highly oriented X‐ray diffraction pattern. These unusual morphological features have been compared with features found in poly[bis(phenoxy)phosphazene] and poly[bis(halophenoxy)phosphazene]polymers. X‐ray diffraction and crystallization results support a smectic‐like

ISSN:0025-116X    

DOI:10.1002/macp.1992.021930210

出版商:Hüthig&Wepf Verlag    

年代:1992

数据来源: WILEY