摘要:

AbstractSilsesquioxanes having 1‐(2‐methylbenzo[b]thien‐3‐yl)‐2‐[5‐(4‐butylphenyl)‐2,4‐dimethylthien‐3‐yl]perfluorocyclopentenes as the pendant groups were synthesized. Photochemical conversion from the open‐ring to the closed‐ring form of diarylethenes chemically bonded to polymers was by 15–25% lower than the conversion of the chromophores dispersed in the same matrix. No appreciable difference in the photoconversion of the fixed chromophores was observed below and above the glass transition temperat

ISSN:1022-1336    

DOI:10.1002/marc.1997.030180801

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe use of two kinds of tantalum(V) aminopyridinato complexes, bis(2‐benzylaminopyridinato)trichlorotantalum(V) and trichlorobis[2,6‐di(phenylamino)pyridinato‐N,N′]‐tantalum(V), activated by methylaluminoxane was studied in polymerization of ethylene. The activities of these homogeneous catalyst systems are comparable to those of metallocenes. The weight‐average molecular weights (M̄w) of the produced polyethylenes are between 60 000 and 200 000 a

ISSN:1022-1336    

DOI:10.1002/marc.1997.030180802

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe pH effect on microsphere formation in the dispersion copolymerization of methyl methacrylate with vinylbenzyl‐terminated poly(acrylic acid) (PAA) macromonomers is studied. The diameter of poly(methyl methacrylate) (PMMA) microspheres is minimum around pH = 8. Dynamic light scattering data indicate that the shell thickness of PAA‐grafted chains shows a maximum around this pH. The degree of expansion of PAA chains drastically affects the particle size of PMMA microspheres during the dispersion copolymerizat

ISSN:1022-1336    

DOI:10.1002/marc.1997.030180803

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA high‐molecular‐weight poly(2,5‐dialkoxy‐p‐phenyleneethynylene) derivative has been prepared by the Heck reaction of 1,4‐bis(2‐ethylhexyloxy)‐2,5‐diiodobenzene and 1,4‐diethynyl‐2,5‐dioctyloxybenzene. The highly luminescent polymer exhibits excellent solubility and can readily be processed into high‐optical‐quality films. The weight‐average molecular weightM̄wwas 240000 g · mol−1, with a polydispersity index of 2.9. Thermal analysis revealed a glass transition around 90°C, and an onset of chemical crosslinking at 130°C. The highM̄wand the remarkable solubility enabled the preparation of liquid

ISSN:1022-1336    

DOI:10.1002/marc.1997.030180804

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractCopolymerizations of diethyl 7‐oxabicyclo[2.2.1]hepta‐2,5‐diene‐2,3‐dicarboxylate (DOHDD) with phenylacetylene (PA) orp‐methoxyphenylacetylene (MeOPA) were successfully performed in chloroform using PdBr2as catalyst. The products of reactivity ratiosr1·r2for poly(DOHDD‐co‐PA) and poly(DOHDD‐co‐MeOPA) are 0.026 and 0.0077, respectively. These values suggest a maximum degree of alternating sequences of 86 and 92% in the two systems, hence a high alternating tendency. It is interesting to note that the present copolymerizations occur by combination of different types of monome

ISSN:1022-1336    

DOI:10.1002/marc.1997.030180805

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe molecular dynamics of dendrimer branches were studied by observing the excimer formation of pyrenyl end‐groups. By a selective synthesis only one pyrene moiety per dendron was attached, resulting in a dendrimer with 3 fluorophors per molecule. The first 3 generations of the dendrimer were synthesized by the convergent‐growth approach. By time resolved measurements of the eximer and monomer fluorescence an increased mobility of the end‐groups was obs

ISSN:1022-1336    

DOI:10.1002/marc.1997.030180806

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe effect of stereoregularity on the thermo‐oxidative degradation of poly(propylene)s, isotactic (IPP) and syndiotactic (SPP), was compared with that of high density polyethylene (HDPE) by means of chemiluminescence (CL). SPP is extremely stable to thermal oxidation and CL signals appeared much later than in IPP and even later than in HDPE. For example, at 160°C the maximum intensity of CL was measured after only 13 min for IPP, 60 min for HDPE and 260 min for SPP. IR spectroscopic results support the conclusions drawn from CL resul

ISSN:1022-1336    

DOI:10.1002/marc.1997.030180807

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe dissociation rate constantkdrelated to the homolytic cleavage of the CON bond formed between a polystyrene (PS) and 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO) is determined by adopting the gel permeation chromatography peak‐resolution method to the styrene polymerization with a PS‐TEMPO adduct as a probe and the radical initiatortert‐butyl hydroperoxide. The result was given by the Arrhenius equation,kd=Aexp(−E/(RT)) withA= 3.0 × 1013s−1an

ISSN:1022-1336    

DOI:10.1002/marc.1997.030180808

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe dissociation rate constantkdof the PS‐TEMPO adduct, where PS is polystyrene and TEMPO is 2,2,6,6‐tetramethylpiperidin‐1‐oxyl, was determined by the gel permeation chromatographic tracing of the evolution of polydispersities at an early stage of styrene polymerization with a model PS‐TEMPO adduct as initiator. The results agree with those obtained by the direct method

ISSN:1022-1336    

DOI:10.1002/marc.1997.030180809

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractPd(II) catalysts with nitrilo ligands and BF4−counter ions give the best results in vinylic polymerization of norbornene. Absolute molecular weight determination of polynorbornene (PN) by means of light scattering and the three‐dimensional shape of PN were also investigated. By correlation of molecular weightsM̄wwith intrinsic viscosity (Staudinger‐index) [η], yield a close to 0.5 exponent for the Mark‐Houwink equation with solvents chlorobenzene and cyclohexane at 25°C expected for polymer molecules with confined conformation. The vinylic polymerization of norbornene with [(CH3CN)4Pd][BF4]2(I) in nitromethane in the presence of ethylene results in PN with narrow molecular weight distribution. No termination and transfer reactions were found, nor any incorporation of ethylene could b

ISSN:1022-1336    

DOI:10.1002/marc.1997.030180810

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY