摘要:

AbstractThe synthesis, characterisation and properties of simple low molecular weight aromatic amide dendrimers is described. The insights into the problems inherent in the synthesis of such systems provided by molecular modelling studies are discussed along with possible strategies for circumventing them. Preliminary results concerning blends of aramid dendrimers with poly(hexamethyleneadipamide) are presented.

ISSN:1022-1360    

DOI:10.1002/masy.19940770104

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe synthesis of three different macromolecular architectures, dendritic segment‐block, layer‐block, and surface‐block copolymers, all of which can be regarded as new types of block copolymers, is discussed. The factors determining the physical properties of each of these unusual materials are studied and related to the dendritic stru

ISSN:1022-1360    

DOI:10.1002/masy.19940770105

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractHighly branched polyphenylenes, polyphenylene ethers, aromatic polyesters and polyamides synthesized from AB2type monomers are reviewed. Polyphenylenes were obtained by aryl‐aryl coupling reactions of 3,5‐dihalo‐phenyl organometallic reagents.13C NMR indicates about 70% branching efficiency. A Tgat 236°C was observed, but the polymer did not form films. Polyethers were prepared by oxidative coupling of 2,4,6‐tribromophenol and 2,4‐dibromophenol. The former monomer gave high molecular weight polymers but the latter monomer did not polymerize well. Condensation of 3,5‐diaminobenzoic acid (I) and 3‐aminoisophthalic acid derivatives in an amide solvent gave lyotropic hyperbranched aromatic polyamides. The GPC indicated a large degree of polymer aggregation in the amide solvent in the absence of a c

ISSN:1022-1360    

DOI:10.1002/masy.19940770106

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe first general single‐step route to dendritic or cascade polyaryl ethers analogous to common linear polyaryl ethers is described. The sodium salts of four AB2monomers each containing a single phenolic hydroxyl group and two aryl fluorides activated toward nucleophilic substitution by carbonyl, sulphonyl, or tetrafluorophenyl moieties are shown to polymerize in hot N, N‐dimethylacetamide. The products are high molecular weight polymers (7000

ISSN:1022-1360    

DOI:10.1002/masy.19940770107

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractSuccessive chloromethylation‐anionic grafting sequences on polystyrene have led to well‐defined hyperbranched macromolecules. Polymers with branching functionalities f>5000 and molar masses over 107g/mol were thus prepared while maintaining a ratio of mass‐ to number‐average molar masses Mw/Mn= 1,1‐1,3. Three series of styrene polymers were prepared by varying the density of grafting sites along the chain, resulting in controllable stiffening of the molecular structure. Characterization of the branched molecules by size‐exclusion chromatography/low‐angle laser light scattering and light scattering confirmed a geometric increase in molar mass for successive generations, and a low ratio of mass‐ to number‐average molar masses. Static and dynamic light scattering experiments showed that the molecules behave like hard spheres in dilute solutions. Measurements in the semidilute range, however, showed a progressive structural stiffening effect as the branching

ISSN:1022-1360    

DOI:10.1002/masy.19940770108

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe synthesis and characterization of a new series of polypropylenimine dendrimers is reported. Using a repetition of the sequence of a Michael addition to a primary amine, followed by a heterogeneously catalyzed hydrogenation, ultra‐pure polypropylenimine macromolecules with molecular weights up to 6912 are synthesized. The reaction sequence allows the preparation of these dendrimers at very large scales, whilst the availability of a simple purification in the sequence affords ultra‐pure samples. The polypropylenimine dendrimers are fully characterized; apart from the first 0.5 generation they are all oils, possess a Tg in the range from −90 to −40 °C, are unexpectedly stable, and their intrinsic viscosity drops after gene

ISSN:1022-1360    

DOI:10.1002/masy.19940770109

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractCascade polymeric architecture possessing internal functionalities was employed for the preparation of metallo‐ and nonmetallo‐MicellaneTMderivatives. Specifically, tetra‐ and dodeca‐o‐carborane superclusters, were obtained via treatment of the corresponding 1stand 2ndgeneration tetra‐ and dodeca‐alkyne, hydrocarbon cascade (MicellaneTM) derivatives with decaborane. Reaction of the same polyalkyne dendritic precursors with Co2(CO)8afforded the benzyl protected, CobaltomicellanesTMpossessing 12 and 24 internal metal centers, respectively. Control of amide‐based, carboxylic acid terminated macromolecular hydrodynamic radius via changes in solution pH was demonstrated. Heterocascade syntheses employing amide and metalligand monomer connectivity were accomplished. The relation of interior cascade reactivity to macromolecular “void vol

ISSN:1022-1360    

DOI:10.1002/masy.19940770110

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractComb‐like polymers have been widely investigated mainly to correlate their structures with the thermal behaviour. Our interests are directed on the synthesis of new types of comb‐like polymers bearing reactive groups in the side chains, main chain or as end groups. One part of the investigations deals with the behaviour of photosensible polymers containing azobenzene, cinnamic acid and mesoionic moieties. The use of enzymes as catalysts for the synthesis of new methacrylic derivatives and for the modification of polymers illustrates a fascinating contribution to polymer chemistry. The classical Diels‐Alder addition was also used for the synthesis and modification of polymers. Finally, the construction of polymers containing rotaxanes in the side chains is pres

ISSN:1022-1360    

DOI:10.1002/masy.19940770111

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractCopolymers and homopolymers containing silicon atoms connected to three and four other silicon atoms have been prepared and characterized. We report the first evidence of dendritic polymers with silicon backbones. Copolymers made from RSiCl3and R1R2SiCl2resemble hybrid materials of polysilyne and polysilanes. Polymers, which contain tetrasilyl‐substituted Si atoms, [(SiMe2)4Si]nand (Si)m(Me2Si)n, have also been synthesized. These molecules appear to be the first hyperbranched polymers, which have applications based on their electronic properties. The properties of these molecules fit into the hierarchy of 1‐D to 3‐D topologies known for Si mate

ISSN:1022-1360    

DOI:10.1002/masy.19940770112

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe synthesis of macrocyclic polystyrene‐block‐poly(2‐vinylpyridine) and macrocyclic polystyrene‐block‐poly(dimethylsiloxane) was carried out by initiation of 2‐vinylpyridine (2VP) and hexamethyl‐cyclotrisiloxane (D3) by difunctional living polystyryllithium followed by coupling with 1,4‐bis(bromethyl)benzene (1,4‐DBX) and dichloro‐dimethylsilane (Cl2SiMe2), respectively. A small portion of the living ABA precursors were protonated to serve as isobaric linear precursors. The linear and macrocyclic block copolymers were characterized by size‐exclusion chromatography (SEC). The ratios of apparent cyclic/linear SEC molecular‐weight maxima versus degree of polymerization (DP) show increases with decreasing DP varying from 0.70 ± 0.03 at high DP ≤ 200 to 0.78 ± 0.044 at low DP (≥60) whereas that of the linear ABA block copolymers decreased. Increases in glass transition temperature (Tg) were also observed for the cyclic PS‐b‐PDMS copolymers with respect to the isobaric linear precursors. The macrocycles were characterized by1H and13C NMR and in the case of macrocyclic PS‐b‐PDMS by29Si NMR as well. Broadening in the NMR absorptions of the macrocyclic block copolymers is general and is similar to that observed for the homopolymers. Differemtial scanning calorimetry (DSC) analysis of the PS‐b‐P2VP macrocycles shows increases in Tg at lower molecular weight as was

ISSN:1022-1360    

DOI:10.1002/masy.19940770113

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY