摘要:

AbstractA critical overview of different synthetic approaches to poly(p‐xylylene)s (PPXs) is coupled with perspectives on particular structure–property relationships and challenging applications. An attempt is made to emphasize the potential of different synthetic approaches to PPXs focused on different applications. Additionally, the synthesis and polymer analogous reactions of PPXs without leaving groups and functionalized PPXs (with leaving groups in thea‐position) serving as processable precursors for non‐processable polymers are ev

ISSN:0323-7648    

DOI:10.1002/actp.1997.010480101

出版商:Akademie Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractComb‐like polymers (CP) based on modified alternating methyl vinyl ether/maleic anhydride copolymer with oligo‐oxyethylene side chains of the type O(CH2CH2O)nCH3have been synthesized and characterized, and complexed with LiNO3to form an amorphous polymer electrolyte. CP/salt complexes showed conductivity up to 10−5S/cm at room temperature. The temperature dependence of ionic conductivity suggests that the ion transport is controlled by segmental motion of the polymer, shown by linear curves obtained in Vogel–Trammann–Fulcher plots. The ionic conductivity maximum moves to a higher salt concentration as the temperature increases. IR results also indicate that the ester in CP might decompose at 140°C and reproduce the maleic an

ISSN:0323-7648    

DOI:10.1002/actp.1997.010480102

出版商:Akademie Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThis paper describes the preparation of new alkynes bearing furanic substituents and their polymerization by catalytic systems based on transition metal halides in order to obtain novel materials with original properties because of the presence of both furan moieties and alternate single and double bonds. However, difficulties arising from the specific reactivity of the heterocycle in our experimental conditions led us to envisage an indirect way to obtain well‐defined products, using an aromatic polymer as the precurso

ISSN:0323-7648    

DOI:10.1002/actp.1997.010480103

出版商:Akademie Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe evidence for biphasic morphology in lightly sulfonated polystyrene (PS‐SSA) ionomers neutralized by bifunctional organic cations (namely, 1,6‐hexanediamine or HDA) is established by comparing their dynamic mechanical behavior, as a function of ion content and degree of neutralization, with that for metal‐neutralized biphasic ionomers. The trends as a function of ion content regarding the transition temperatures and intensities of the HDA‐neutralized ionomers parallel what is observed for metal‐neutralized ionomers, in particular polystyrene‐based ones. A small‐angle X‐ray scattering peak, identified as an “ionomer peak”, is observed in the PS‐SSA‐HDA ionomer of the highest ion content studied. Furthermore, it was observed that partial neutralization affects the cluster phase more strongly than the matrix phase. This can be explained by the contribution of the acid groups to the matrixTg, and their ability, when present in large amounts, to affect the ionic interaction strength or facilitate ion hopping, which influences

ISSN:0323-7648    

DOI:10.1002/actp.1997.010480104

出版商:Akademie Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractTopological considerations concerning the ratio of linear, imperfectly branched, dendritic and terminal units in hyperbranched polymers based on AB2, AB3and ABm(m≥2) type monomers are summarized. The reaction of AB2monomers with a core molecule of the structure Bfis also treated. For larger hyperbranched polymers based on AB2monomers the fraction of terminal units has to be equal to the number of dendritic units. A general expression for the degree of branching (DB) is derived for AB2systems, which is based on the number of dendritic and linear units. The expression is valid for low molecular weight as well as high molecular weight hyperbranched polymers in contrast to the commonly used expression based on dendritic, linear and terminal units. DB may not exceed 0.5 in hyperbranched polymers based on AB2systems (0.44 in AB3systems). Furthermore, a general expression for DB in hyperbranched polymers based on ABmmonomers is derived. Consequences for signal ratios in NMR‐spectra of hyperbranched polymers are discussed. The expressions presented allow verification of NMR‐integration ratios obtained experimentally on the basis of model comp

ISSN:0323-7648    

DOI:10.1002/actp.1997.010480105

出版商:Akademie Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe X‐ray long periods from high molecular weight injection molded polyethylene (PE) with a shish‐kebab structure have been compared with values derived from electron micrographs. It is shown that while small angle X‐ray scattering (SAXS) presents two long periods, the direct measurements from transmission electron microscopy (TEM) furnish only the lower SAXS periodicity. In an attempt to clarify this discrepancy of results, laser light diffraction and Fourier transformation of electron micrographs have been undertaken. Using this method two long periods are found in all regions investigated. Results are discussed in terms of the role played by the structured or “weakly crystalline” interlamellar parts, containing a lower electron density, which are neglected by the small angle scattering of X‐rays and which give rise in particular regions to larger scattering pe

ISSN:0323-7648    

DOI:10.1002/actp.1997.010480106

出版商:Akademie Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe viscoelastic properties of fourteen syndio‐ and isotactic polypropylenes (PPs) were measured in the molten state at several temperatures by means of oscillatory rheometry. Metallocene catalysis allows the control of molecular mass of both PP families and provides narrow molecular mass distributions (MMD) with a polydispersity of about 2. The validity of the Arrhenius and WLF equations for PP was checked. Syndio‐ and isotactic PP follow Arrhenius behavior but exhibit different activation energies of flow. From the dynamic shear moduli, viscoelastic parameters were determined and correlated with molecular mass. The dependence of the zero shear viscosity on the weight average molar mass exhibits the well‐known scaling relation. Stereoregularity has an important effect on the viscoelestic behavior of PP

ISSN:0323-7648    

DOI:10.1002/actp.1997.010480107

出版商:Akademie Verlag GmbH    

年代:1997

数据来源: WILEY