摘要:

AbstractThe synthesis of highly uniform (1,08 ≤Mw/Mn≤ 1,13) telechelic poly(ε‐caprolactone) terminated at both ends with OH groups and its derivatization leading to poly(ε‐caprolactone) with pyrene end‐groups are described. The synthesis, carried out in THF at room temperature, involves initiation with (CH3CH2)2AlO(CH2CH2O)3Al(CH2CH3)2, leading to poly(ε‐caprolactone) macromolecules growing at both ends. The active centers were deactivated with acetic acid, giving macromolecules with OH end‐groups. Reaction of α,ω‐dihydroxypoly(ε‐caprolactone), HO‐poly(εCL)‐OH, with 4‐(1‐pyrenyl)butyryl chloride yields α,ω‐di‐1‐pyrenylpoly(ε‐caprolactone), Py‐poly(εCL)‐Py. Polymers are characterized by GPC,1H NMR, and UV spectroscopies. The UV spectra of polymers with pyrene end‐groups are

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920701

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractPoly(p‐trimethylsiloxystyrene)(1a), poly[p‐(tert‐butyldimethylsiloxy)styrene](1b), poly[p‐(trimethylsiloxy)‐α‐methylstyrene](1c), poly[p‐(tert‐butyldimethylsiloxy)‐α‐methylstyrene)(1d)and poly{p‐[2‐(tert‐butyldimethylsiloxy)ethyl]styrene]}(1e)were prepared by free‐radical or cationic polymerization of the corresponding monomers. Poly{[p‐[2(trimethylsiloxy)ethyl]styrene]‐co‐[p‐(2‐hydroxyethyl)styrene]}(2a)was synthetized by anionic polymerization of the corresponding trimethylsilylated monomer, followed by acid hydrolysis of the resulting polymer. Poly{[p‐[2‐(trimethylsiloxy)ethyl]styrene]‐co‐[p‐(tert‐butoxycarbonyloxy)styrene]}(2b)were prepared by free

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920702

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThree isomers of methylstyrene derivatives with a dimethylamino group inorthoposition to the methyl group were prepared through the coupling reaction of the corresponding Grignard reagent and vinyl bromide using a Pd(0) catalyst, and their radical and anionic polymerization was examined. Monomer reactivity ratios in the radical copolymerization with styrene indicate that 3‐dimethylamino‐4‐methylstyrene (3‐DMA‐4‐MS) and 4‐dimethylamino‐3‐methylstyrene (4‐DMA‐3‐MS) have a higher reactivity than styrene, while the reactivity of 3‐dimethyl‐amino‐2‐methylstyrene (3‐DMA‐2‐MS) is lower than that of styrene. The13C NMR chemical shift of vinyl carbons as well as thee‐values indicate that the electron density at the vinyl carbons of 3‐DMA‐4‐MS and 4‐DMA‐3‐MS is increased by the electron donating effect of the dimethylamino group, which results in lower reactivity of the monomers in anionic polymerization. The anionic copolymerization with 1,1‐diphenylethylene gave an alternating copolymer. In the anionic polymerization of 3‐DMA‐2‐MS, proton transfer reaction from the methyl group to the propagating chain end occurred

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920703

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA series of liquid‐crystalline polystyrene derivatives with ω‐(4‐(4‐fluorophenylazo)phenoxy)‐alkoxy pendant groups have been synthesized and characterized. Homologues with four or more methylene units in the spacer chain exhibit smectic liquid‐crystalline phases, while the homologue with three methylene units forms an amorphous glass. The smectic A‐isotropic (SA‐I) transition temperatures show a marked odd‐even effect as a function of the parity of the spacer chain. This odd‐even behaviour is also found in the variation of ΔS/Rat the SA‐I transition across the series. A marked hysteresis between the transition temperatures determined on heating and the transition temperatures determined on cooling is observed. A molecular interpretation of thes

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920704

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractLinear polyethylenes covering the range from high to low density were prepared in gas phase using an MgCl2‐supported Ziegler catalyst deposited on silica (bisupported catalyst). The comonomer used was 1‐butene. Molecular weights are dependent both on 1‐butene concentration and hydrogen pressure. The interaction of these two factors can be interpreted by the enhancement of the transfer reactions after 1‐butene in

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920705

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe reactivity under UV light and at room temperature of two series of photo‐crosslinkable silicone polymers containing pendant cinnamic or α‐cyano‐β‐styrylacrylicSystematic name: 2‐cyano‐5‐phenyl‐2,4‐pentadienoic.(CSA) esters was examined by means of UV spectroscopy. Two types of behaviour were evidenced on the basis of qualitative spectrum observation and quantitative measurements of reaction rates. Polymers withtrans‐cinnamic pendant groups were found to undergo during the first moments of 280 nm irradiation a fast photo‐isomerization, preceding the dimerization process which takes place with a smaller rate. The mobility of the reactive cinnamic chromophores attached to the highly flexible silicone main chain leads to a collision‐controlled process contrasting with the behaviour of the polymers containing more polar CSA esters. In this case, a clean dimerization with high reversibility suggests a matrix‐controlled process. This is supported by kinetic data indicating a levelled reactivity for several polymers containing diff

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920706

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper reports on interface reactions between polybutadiene epoxide (PBDE) and highly dispersed oxides (SiO2, Al2O3) during composite formation. Mechanisms of these reactions are discussed in dependence on the nature and concentration of active surface species (Brönsted‐ and Lewis‐acid sites). Conclusions regarding the macroconformations of chemisorbed PBDE in the system PBDE/SiO2can be drawn by determination of interface conversion between epoxide and silanol gr

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920707

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe thermal solid state polymerization was analysed for topospecifically deuterated derivatives of 2,4‐hexadiynylene di‐p‐toluenesulfonate (PTS). Deuteration of the methylene groups close to the diacetylene‐monomer triple bonds influences drastically the length of the induction period and the reaction‐rate constants in the autocatalytic period. These peculiarities were investigated by the combination of dielectric permittivity measurements with differential scanning calorimetry and gravimetrical analyses of the solid state polym

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920708

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe catalytic activity of polystyrene‐ and polyphosphazene‐supported monosulfoxides and oligo(oxyethylene)s was investigated in the Williamson alkylation of sodium phenoxide with 1‐bromooctane in 1,4‐dioxane at 75°C. Polymer‐supported monosulfoxides are less efficient than low‐molecular‐weight species. Polymer‐supported oligo(oxyethylene)s with pseudo‐crown‐ether structures show a polymer effect, which may even be stressed by the presence of onium unit

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920709

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractLinear and star‐branched chains withF= 4 − 12 arms andN= 125 − 7685 segments covering points of a tetrahedral lattice were generated by use of a pivot algorithm. For largeN, the acceptance fractions f̄ of attempted moves may be described by a power law f̄ =A· (N− 1)−α. Clearly, the factorAdecreases with increasing functionalityF, but the exponent α is independent of the number of arms and equal to the value obtained for linear chains, α ≈ 0,1. Due to the influence of the hard‐core (centre) of the star, the acceptance fraction f̄ for smallNis lower than predicted by the scaling law, yielding a stronger dependence onFthan for large chains. Meansquare dimensions, i. e. mean‐square radius of gyration, mean‐square end‐to‐end distance and mean‐square centre‐to‐end distance obey a power law dependence on chain‐length (N− 1), the exponent being ≈ 1,184 for 245 ≤N≤ 7685 in all cases; alternatively, the (quadratic) dimensions may be described by a corrected scaling law (N− 1)2v· (C0+C1· (N− 1)−Δ)withv= 0,588 and Δ ≈ 0,5 as proposed by renormalization group theory for linear chains. The shape asymmetry of star‐branched polymers (with the same total number of segments each) decreases with increasing number of arms, but is still

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920710

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY