摘要:

AbstractLight scattering, osmometric and viscometric studies were carried out with dilute solutions of well‐defined poly(4,4′‐isopropylidenediphenyl carbonate)‐block‐polystyrene multiblock copolymers, PC‐b‐PS, in non‐selective and selective solvent systems. The influence of copolymer composition, numbers and lengths of blocks in the copolymer chain and type of solvent used on the dilute solution properties, conformation of the investigated multiblock copolymers and on some thermodynamic parameters are discussed. The intrinsic viscosity [η], the unperturbed dimension 〈R02〉/Mand the second virial coefficientA2are larger in non‐selective solvents than expected from the averaged values of the parent homopolymers. In benzene, a selective solvent for polystyrene, formation o

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920111

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA new series of optically active liquid‐crystalline comb‐branch copolymers was prepared from (S‐2‐[2‐(4‐methoxy‐4′‐biphenylyloxy)‐1‐methylethoxy]ethyl methacrylate (1) and the nematogenic monomer 4‐cyanophenyl 4‐(6‐acryloyloxyhexyloxy)benzoate (2). These copolymers are characterised by the chiral centre being positioned in the flexible spacer. The copolymers form chiral nematic phases with temperature‐dependent reflection colours at low chiral monomer compositions, and crystalline phases at higher compositions. One of the copolymers of intermediate composition forms a smectic phase in addit

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920112

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe addition reaction of 3,6‐dioxaoctane‐1,8‐dithiol with various diisocyanates, proceeding by addition of 1,4‐diazabicyclo[2.2.2.]octane as basic catalyst, was investigated. That way, NCO‐and SH‐terminated linear thiocarbamate telechelics (containing NHCOS‐groups) were synthesized. The structures were evaluated by IR and13C NMR spectroscopy. Results show that side reactions of the NH protons with isocyanate (forming allophanates) can be excluded. The NCO‐terminated prepolymers are suitable to be used as participants in common isocyanate reactions. Thus, by treating with allyl alcohol, 2‐hydroxyethyl methacrylate or diallylamine, they can be transformed into telechelics with olefinic end‐groups (5, 6, 7). The products were characterized by their number‐average mol. wts. (VPO) and elemental analysis, and the expected chemical structures were confirmed by char

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920113

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe UV absorption spectrum of an equimolar mixture of 3,6‐dioxaoctane‐1,8‐dithiol (4) and ethylene glycol divinyl ether (1) shows a broad charge‐transfer absorption in the range of 380–420 nm. The absorption band is destroyed in the course of two hours, and the absorption spectrum is identical with that of the poly(thioether) (5). The number‐average molar massM̄nof such a reaction product amounts to 4 300 g · mol−1after 24 h. Addition of chloranil or 1,4‐diazabicyclo[2.2.2]octane (DABCO) leads to an effective inhibition of the spontaneous polymerization. DSC investigations confirmed the exp

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920114

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA new rotational viscometer is presented which can be operated up to 2 000 bar and a maximum shear stress of 420 Pa. It allows, for the first time, to investigate the non‐Newtonian flow behaviour of moderately concentrated polymer solutions. Results of measurements with two representatives of the system 2‐propanol/poly(butyl methacrylate) with weight‐average molecular weightsM̄w= 520 000 andM̄w= 2 050 000, and ratios of weight‐ to number‐average molecular weightsM̄w/M̄n= 1,08 andM̄w/M̄w= 1,23, resp. in the region of moderate polymer concentrations are reported. For a ca. 7 wt.‐% solution of the higher‐molecular‐weight polymer one obtains viscometric relaxation times τ0varying from 1 to 100 ms in the region from 1 to 2 000 bar and from 40 to 75°C; at the lower temperature the application ofpcan raise τ0by one order of magnitude. The steady‐state shear compliance (proportional to τ0/η0, where η0is the zero‐shear viscosity), is independent of pressure of varies only slightly. For the present system, which gels thermoreversibly upon cooling, η0and τ0as a function of temperature and pressure can be well represented by t

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920115

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA series of ultraviolet‐induced photocrosslinkable polyurethane acrylates was synthesized. They are composed of a polyether [poly(propylene oxide) or poly(tetramethylene oxide)] soft segment and two terminal hard segments derived from 2‐hydroxyethyl methacrylate and a diisocyanate. Based on stress‐strain and DSC measurements of their UV‐cured materials, relations between their structure and physical properties were investigated systematically. The results show that parameters which increase the content of hard segments and the crosslinking density of UV‐cured materials lead to an increase in Young's modulus and stress at break accompanied by a decrease in elongation at break. The glass transition temperature of the polyether soft segment is determined mainly by the type and molecular weight of the polyether, due to a two‐phase

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920116

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe peculiar structural modifications of Nylons 8, 10 and 12 prepared by crystallization from solutions and reported as α*, were studied by differential scanning calorimetry (DSC) and thermomicroscopy, supported also by some X‐ray diffraction (XRD) measurements. The results indicate that the phase transition shown by the α*‐forms of the Nylon 8–12 series exhibits the characteristics of a melting immediately followed by crystallization into γ‐form, rather than of a α* → γ solid‐solid transition. When the γ‐crystallization is concluded, the melting of this form takes place. DSC and XRD data demonstrate that the α* → γ transition is irreversible. The changes in the DSC traces of the Nylon 8 – 12 series were interpreted as indicative of a gradual stability increase of the α‐form in comparison with the corresponding α*‐form, depending on the increase of the number of methyle

ISSN:0025-116X    

DOI:10.1002/macp.1991.021920117

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY