摘要:

AbstractComb‐like liquid‐crystalline polyacrylate,1, containing 4′‐cyano‐4‐biphenylyl mesogenic groups and forming a reentrant nematic (Nr) phase, as well as its mixture with 4‐cyano‐4′‐hexyloxybiphenyl were studied by X‐ray diffraction. X‐ray diffraction patterns of magnetically‐oriented samples and the micro‐densitometer curves obtained from them allowed to observe the distortion of the layers with orthogonal packing of the mesogenic groups in the Nrphase. These results are compared with electrooptical data obtained earlier. As a result a domain formation with tilted arrangement of the mesogenic groups in

ISSN:0025-116X    

DOI:10.1002/macp.1990.021911101

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractBlends of the diglycidyl ether of poly(ethylene glycol) (1)IUPAC name of1: α‐(2,3‐epoxypropyl)‐ω‐(2,3‐epoxypropoxy)poly(oxyethylene).and the triglycidyl ether of glycerol (2)IUPAC name of2: 1,2,3‐tris(2,3‐epoxypropoxy)propane.were crosslinked in the presence of LiClO4which seems to act as both a catalytic curing agent and as the source of the ionic charge carriers. The cured film showed a rather high ionic conductivity of about 10−5S/cm at 25°C. The effect of composition, salt concentration and molecular weight of1on the conductivity and on the glass transition temperatureTgof the cured1/2LiClO4system was examined. The conductivity increased whereasTgdecreased with increasing1/2ratio. An increase of the molecular weight of1favoured the lowering ofTgand thus raised the conductivity. As to the effect of LiCIO4concentration, the maximum conductivity occurred at about 5 wt.‐% of LiClO4andTgincreased with increasing LiClO4content. The temperature dependence of the conductivity followed the Vogel‐Tamman‐Fulcher equation. This indicated that the ionic conductivity is effected by the cooperative segmental motion. All of the prepared specimens were found to be amorphous. They were mechanically strong films and showed rubber‐elas

ISSN:0025-116X    

DOI:10.1002/macp.1990.021911102

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractA preliminary investigation on the influence of the coagulation process on the solid‐phase structure of poly(1,3,4‐oxadiazole‐2,5‐diyl‐1,4‐phenylene) (1) is reported. Interesting correlations between the method of coagulation of the polymer from sulfuric acid solution and the structure which develops, as observed by thermal analysis, X‐ray diffraction, infrared spectroscopy, and optical microscopy are found. A new method for the preparation of highly crystalline spherulites of1is described. This method allows to grow a relatively large number of “single spherulites”, because coagulation and crystallization induced by a non‐solvent may be stopped before

ISSN:0025-116X    

DOI:10.1002/macp.1990.021911103

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe aqueous‐phase dispersion polymerization ofN,N′w‐methylenebis(acrylamide) (MBA) in the presence of various additives was kinetically investigated at 50°C by conventional gravimetric and dilatometric methods. The rate of polymerization is found to be proportional to the concentration of sodium 1,2‐bis(2‐ethylhexyloxycarbonyl)ethanesulfonate (AOT) raised to the power of 0,42 (conc. of emulsifierT

ISSN:0025-116X    

DOI:10.1002/macp.1990.021911104

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractCyclic oligo[oxymethyleneoligo(oxyethylene)]s and linear poly[oxymethyleneoligo(oxyethylene)]s have been prepared by condensation of tri‐, tetra‐, penta‐ and hexaethylene glycols, including a number of samples not reported previously. The linear and cyclic products were characterised using nuclear magnetic resonance and gel‐permeation chromatography, and then studied using differential scanning calorimetry. Even‐odd effects in the values of the melting points and enthalpies of fusion of the samples are dem

ISSN:0025-116X    

DOI:10.1002/macp.1990.021911105

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe reaction betweenN‐isobutylallylnadimide (NIBANI) andN‐isobutylmaleimide (NIBMI) was taken as a model reaction to obtain insight into the curing mechanism of polymeric alloys and composites consisting of bis‐ or tris(allyl)nadimides and bismaleimides. The reaction between NIBANI and NIBMI is not catalyzed by boron trifluoride etherate, neither at room temperature nor in refluxing methylene chloride. The thermally induced reaction (200°C) between NIBANI and NIBMI in equimolar quantities gives an indirect proof for the occurrence of an ene reaction. The high reactivity of the ene reaction product to undergo further Diels‐Alder reaction was proved by GPC and direct inlet mass spectral

ISSN:0025-116X    

DOI:10.1002/macp.1990.021911106

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractA combined X‐ray diffraction and electron microscopy study was carried out on both the solution‐grown crystals and oriented films of nylons 3/5/7 and 7/5/3. These regular odd‐odd‐odd terpolyamides have such sequence of amide groups along the chain that they have to be aligned parallel in order to form every hydrogen bond without strain. It was found that a layered α‐structure with hydrogen‐bonded sheets made up of parallel chains in fully extended conformation is adopted in both cases. These results are not necessarily generalized to odd‐numbered nylons where an antiparallel alignement of chains is compatible with the formation of hydrogen bonds. Chain‐folded lamellar crystals obtained from solution were investigated by electron diffraction and their surface topology examined by polymer decoration with polyethylene. A bimodal orientation of hydrogen‐bonded sheets within the lamella is assumed to occur in order to account for the obtained decorating patterns. Either way, chain foldings are not contained in such sheets but intersect them at an

ISSN:0025-116X    

DOI:10.1002/macp.1990.021911107

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractEthyl α‐acetoacetoxymethylacrylate (1) was prepared by reaction of diketene and ethyl α‐hydroxymethylacrylate which was obtained from the reaction of triethyl phosphonoacetate and an aqueous solution of formaldehyde.1contains 27% of the enol tautomer. The polymerization of1in benzene initiated with dimethyl 2,2′‐azoisobutyrate (2) was investigated kinetically. The overall activation energy of polymerization was determined to be 84,8 kJ/mol. The polymerization rate (Rp) at 50°C is expressed byRp=k[2]0,5[1]1,1. From an electron spin resonance study, the polymerization system was revealed to involve persistent propagating poly(1) radicals. The rate constants of propagation and termination were estimated to bekp= 300 andkt= 1,0 · 1061 · mol−· s−at 60°C, respectively, using the polymer radical concentration and assuming stationary state conditions. Copolymerization of1(M1) and styrene (M2) was examined at 50°C, and the following copolymerization parameters were obtained;r1= 0,28,r2= 0,22,Q1

ISSN:0025-116X    

DOI:10.1002/macp.1990.021911108

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe relaxation processes in atactic poly(benzyl methacrylate) were studied by means of dielectric measurements. Beside the α‐ and β‐relaxation processes due to the segmental motions of the main chain and of the entire side chain, respectively, a process designated as γ was found to occur in the temperature range between −60°C and 0°C. For the γ‐relaxation, the time‐temperature superposition principle is applicable. A linear relationship between temperature and the relaxation frequencyfmor shift factoraTwas found. Apparent activation energies estimated from the temperature dependence offmandaTare 50 and 53 kJ · mol−1, respectively. The γ‐process is considered to result from the movement of the benzyl gr

ISSN:0025-116X    

DOI:10.1002/macp.1990.021911109

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe emulsion polymerization of butadiene was investigated with sodium dodecyl sulfate as emulsifier, and the results were compared with those obtained with the industrial‐grade emulsifier Dresinate 214. Limited coagulation was observed in both cases, caused by the high ionic strength of the aqueous phase. Sodium dodecyl sulfate was found to be a better stabilizer than Dresinate 214. The average rate per particle in interval II (corresponding to the linear portion of the conversion vs. time curve) depends strongly on particle size, but not on recipe parameters used to vary the final particle diameter, such as the type and amount of emulsifier and ionic strength. The dependence of particle number per volume of waterNon initiator ([I]) and emulsifier concentration ([E]) is usually expressed as the exponent in the empirical relationshipN∼ [I]x· [E]y. Promoting coagulation by increasing the ionic strength decreasesxtowards zero, whileyincreases sharply. Increasing [I] at constant [E]and constant ionic strength induces limited coagulation, presumably because the rate of emulsifier adsorption becomes insuffic

ISSN:0025-116X    

DOI:10.1002/macp.1990.021911110

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY