ISSN:1022-1360    

DOI:10.1002/masy.19971180103

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractIn this paper we attempt to trace the course of development of our work on aromatic copolyesters starting in 1963 with the successful polymerization of p‐hydroxybenzoic acid and its aromatic copolyesters and continuing up to the present. In so doing a number of interesting issues are identified which provide us with important insights into the rapidly changing research environment of the past 30 years. Perhaps more importantly, some of the key requirements for successfully carrying out research into the 21st Century within a University framework begin to emerge. As part of the overview, a brief retrospective of work over the last 40 years in the field of high temperature polymers is given to provide a suitable background to the motivation for our researc

ISSN:1022-1360    

DOI:10.1002/masy.19971180104

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe conformation of chain molecules participating variously in the formation of liquid crystalline mesophase has been elucidated. Two examples are mentioned: (1) the side chain flanking the α‐helical backbone of polypeptides, and (2) the spacer joining mesogenic units in mainchain liquid crystals. Flexible segments play an important role in determining thermodynamic properties of these syste

ISSN:1022-1360    

DOI:10.1002/masy.19971180105

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractQuasi‐equivalent building blocks are chemically identical subunits which self‐control their shape by switching between different conformational states. Classic biological examples are the flat‐tapered and conical protein coats which jacket nucleic acids during the self‐assembly of rod‐like and icosahedral viruses, respectively. This paper advances the hypothesis that monodendrons can act as synthetic quasi‐equivalent building blocks. The rational design of flat‐tapered and cone shaped quasi‐equivalent monodendrons and their use in the construction of three dimensional supramolecular and macromolecular rod‐like and spherical systems demonstrates the above hypothesis. Mechanisms which interconvert the spherical systems into rod‐like ones by using the same monodendron building blocks, thus demonstrating their quasi‐equivalence

ISSN:1022-1360    

DOI:10.1002/masy.19971180106

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractMetallocene/MAO catalysts are useful for the production of syndiotactic polystyrene ‐ a new class of high performance polymers. The melting point of the obtained syndiotactic polystyrene depends on the metallocene used and can reach up to 275 °C. In the past, the most active catalysts in polymerization have been half‐sandwich titanocenes such as CpTiCl3and Cp*TiCl3. If the chlorinated compounds are changed into the fluorinated compounds as CpTiF3and Cp*TiF3, the activity increases by a factor of 5 to 100. The fluorinated titanocenes are more stable at higher temperatures and need a lower MAO excess in order to obtain optimal activities.Polymers obtained with the unsubstituted CpTiF3show melting points which are 17 °C lower than those synthesized by pentamethylcyclopentadienyltitaniumtrifluoride. Especially Cp*TiF3shows a much higher activity and, compared with the chlorinated compound, gives polymers with a higher molecular weight. Substituted cyclopentadienyltitanocenes have even higher activities. Ethene/styrene copolymers can be obtained by catalysis with zirconocene comp

ISSN:1022-1360    

DOI:10.1002/masy.19971180107

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe MgCl2supported half titanocenes and Ti(4, 4, 4‐trifluoro‐1‐phenyl‐1, 3‐butanedionato)2Cl2catalysts were synthesized and applied to propene polymerization. Without supporting on MgCl2, those complexes displayed almost no activity even using methylaluminoxane (MAO) as cocatalyst. When supported on MgCl2, on the other hand, the resulting catalysts could be activated by ordinary alkylaluminums to yield polypropene in fairly high yields. The catalyst isospecificity was markedly improved by the addition of a suitable L

ISSN:1022-1360    

DOI:10.1002/masy.19971180108

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractSeveral nucleic acid analogues as shown in Scheme 1 were synthesized by alternating copolymerization of nucleoside analogues with maleic anhydride or acrylic anhydride. These polymers showed similar physicochemical properties to those of the natural polymers, such as base‐pairing and base‐stacking. Polymer 3U, for example, formed 1:1 complex with poly(adenylic acid) by base‐pairing. Polymer4Ashowed 33% of hypochromicity compared with the UV‐absorption of adenosine due to the base‐stacking. Polymer5catalyzed the cleavage of DNA and the hydrolysis of phosphodiester with a rate acceleration of 103compared with the uncatalyzed

ISSN:1022-1360    

DOI:10.1002/masy.19971180109

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA new class of multifunctional polymers based on poly(1, 6‐heptadiyne) derivatives with various functional groups such as carbazole unit for photoconductive polymers and nonlinear optical (NLO) chromophores for NLO polymers were synthesized by metathesis polymerization. The polymerizations were carried out with MoCl5‐ and WCl6‐based catalysts. The catalytic activity of MoCl5was found to be greater than that of WCl6. The resulting polymers exhibited photoconductivity and large optical nonlinearity. These conjugated polymers have good solubility in common organic solvents, long‐term stability toward air oxidation, and high electrical condu

ISSN:1022-1360    

DOI:10.1002/masy.19971180110

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe synthesis of aromatic polyamides, namely poly(p‐phenylenetere‐phthalamide) and poly(p‐benzamide),viaphosphorylation reaction has been thoroughly investigated. The effect of reaction temperature, concentration of monomers and reactants, type and concentration of salts, amount of the activator and its stepwise addition have been considered and the optimum reaction conditions found. The resultant synthesis of the above polymers, also in connection with the high purification techniques of all components of the reaction mixture, allowed to reach the highest molecular weights obtained so far by this syntheti

ISSN:1022-1360    

DOI:10.1002/masy.19971180111

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe polyaddition reaction of bisimidazolines with α, ω‐dicarboxy polyamide‐12 in the bulk at 200–240°C (oligomer coupling reaction) produces high MW polymers, while degradation reactions were observed with aliphatic polyesters. The chain extension of a α, ω‐dicarboxy polyamide‐polyoxytetramethylene‐polyamide oligomer with 2, 2'‐tetramethylene‐bis(imidazoline) yielded a poly(poly‐ether‐block‐polyamide). 4‐substituted and 4, 4‐disubstituted bis(5(4H)oxazolinones) are efficient coupling agents for amino‐terminated oligomers, allowing the rapid synthesis of copolymers containing polyether and polyamide blocks. The chemistry of these chain‐coupling reactions has been studied by NMR. DSC shows the phase separation between the hard (polyamid

ISSN:1022-1360    

DOI:10.1002/masy.19971180112

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY