摘要:

AbstractThe tensio‐active properties of different types of diesters can be used to synthesize two‐dimensional model networks at the interface between oil and water. We have systematically studied rubber‐elastic, glass‐like and transient membranes, which are stabilized and crosslinked by physical or chemical contacts. The kinetics of surface gelation and the mechanical properties of the crosslinked membranes were investigated by measuring two‐dimensional rheological parameters, such as the shear modulus or the surface viscosity. The experimental data of these investigations are in fairly good agreement with the theoretical predictions of percolation theories. Further informations on the molecular structure of the crosslinked membranes can be obtained from electron spin resonance (ESR) measurements. Using spin labels of significantly different sizes, which are diffusing from the aqueous environment into the oil phase, it is possible to determine the average mesh size of the interfacial network structure. The systematic study of these ultrathin membranes offers new insights into aspects of current research, and opens interesting new technical app

ISSN:1022-1352    

DOI:10.1002/macp.1995.021960101

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractMixing enthalpies and Gibbs energies of liquid propylene oxide oligomers with hydroxyl and methoxy end groups and of block and statistical cooligomers of ethylene oxide and propylene oxide in tetrachloromethane are obtained by microcalorimetry and vapour pressure measurements. The thermodynamic excess quantities ΔH, ΔGEand ΔSEof mixing are influenced by induced dipol interactions of the ether segments with CCl4and by the hydrogen bond interactions of the OH end groups. An expanded theoretical treatment using the Huggins approach of quasichemical equilibrium between the contacting segment surfaces is successfully applied on the experimental resul

ISSN:1022-1352    

DOI:10.1002/macp.1995.021960102

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractRheo‐optical techniques of determining flow‐birefringence Δn′ and flow‐dichroism Δn″ were employed to investigate a Tobacco Mosaic Virus (TMV) solution under steady‐state and relaxation conditions to obtain further information about molecular dynamics in terms of local and global orientation and flexibility. These effects were investigated in a concentration range of 0,5 g/L ⩽c≦ 2,89 g/L, i.e. below and above the critical overlap concentrationc* = 2,45 g/L. Although some aggregation was unavoidable it was determined that in the region ofc* the dynamic behaviour was not influenced by varying the concentration. Furthermore it was shown that these aggregates naturally appearing in TMV are sensitive to shear force and dissolve at shear rates above 1 s−1. Beyond the critical shear rate this rodlike molecule should show a good agreement of the orientation angles determined through dichroism and birefringence and a constant ratio Δn″/Δn′ which in fact was found. This reveals experimentally that in spite of the sensitivity to different length scales dichroism and birefringence exhibit similar responses to shear forces for rigid and mo

ISSN:1022-1352    

DOI:10.1002/macp.1995.021960103

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractTwo synthetic routes to copolymers7of methyl methacrylate (MMA) with 2‐(N‐pyrrolyl)ethyl methacrylate (PEMA,11) are compared. Copolymerization of MMA(4)with 2‐bromoethyl methacrylate (BEMA,3) leads to a precursor copolymer5. The reactivity ratios are close to unity (rMMA= 0,90,rBEMA= 0,92). The polymer‐analogous reaction of5withN‐pyrrolylpotassium(6)runs to 99% conversion of the BEMA units. The synthesis of PEMA(11)is presented. The reactivity ratios of copolymerization of this monomer(11)with MMA(4)are determined torMMA= 1.05 andrPEMA= 1,65. Copolymers7are further characterized by1H nuclear magnetic resonance, infrared spectroscopy, gel‐permeation chromatography and differential scanning

ISSN:1022-1352    

DOI:10.1002/macp.1995.021960104

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the course of the reaction of polystyryllithium (PSL) and 2‐polystyryl‐1,1‐diphenylethyl‐lithium (PSDPEL) with methyl acetate (MA), methyl benzoate (MB) and acetyl (ACI) and benzoyl (BCI) chlorides as coupling agents (CA), the quantity of the product of combination P2Y, where P2corresponds to double molecular weight (MW) of the initial PS or PSDPE and the CA residue is referred to as Y, strongly depends on the nature of CA, and to a lower degree on the CA/PSL (PSDPEL) ratio and the nature of the solvent (benzene or THF). The maximum yield of P2Y from the reaction of MA and PSL did not exceed 80%, and 12% for MA and PSDPEL. It was shown using CD3COOCH3and 500 MHz NMR that this incomplete conversion is due to a side reaction of PSL or PSDPEL with the D(H) atoms of the methyl group of MA, proceeding simultaneously with the main reaction and yielding PSD(H) or PSDPED(H). Using a special approach, the polymeric ketone corresponding to the first stage of this reaction can be obtained; its yield was in the case of PSL and MA higher than 50%. For the PSDPEL‐MA system, the product of the reaction, based on NMR data, consists of approximately equal portions of the polymeric ketone and the product resulting from the side reaction, i.e., PSDPE‐H. In the latter case the sterically hindered polymeric ketone did not react with excess PSL or PSDPEL. Products of the reaction of PSL or PSDPEL with MB dit not contain PSH or PSDPEH, r

ISSN:1022-1352    

DOI:10.1002/macp.1995.021960105

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe formation of freezing water as a function of temperature and time has been studied in polyelectrolytes and in cellulose. In such systems, a portion of the sorbed water is not crystallizable under normal conditions. However, it was observed that in rapidly cooled systems the ratio between freezing and non‐freezing water is variable and depends on the annealing temperature. The difference between the saturated concentration of freezable water and the concentration of freezing water which is formed immediately after the rise of the sample's temperature is dependent on the materials geometry. It is assumed that the rise of the annealing temperature above room temperature increases the amount of mobile water which can crystallize. By comparing the measured concentration of freezing water with desorption analysis, the average distance of transportation of mobile water for sodium carboxymethylcellulose was calculated as 8–10

ISSN:1022-1352    

DOI:10.1002/macp.1995.021960106

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe syntheses of tetraphenylporphyrins1b, d, econtaining four methacryloyloxy or 2,4‐hexadienoyloxy substituents and phthalocyanines2b, dcontaining four methacryloyloxy substituents are described. Copolymerizations with styrene in solution were investigated in detail, and the compositions and molecular weights of the copolymers were determined. In addition, homopolymerizations in solution were carried out. After coating on quartz or KBr plates, the thermal and photochemically induced homopolymerizations were investigated fundamentall

ISSN:1022-1352    

DOI:10.1002/macp.1995.021960107

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA new photocrosslinkable polymer designed for application in second harmonic generation has been prepared and tested for frequency doubling of IR lasers. The polymer is based on a colorless polyurethane with pendant tolane nonlinear optical chromophores that carry a polymerizable styrene moiety at their extremities. Photocrosslinking is achieved by irradiation of films containing a small amount of a bleachable radical photoinitiator. The effect of photoinduced radical crosslinking on the mobility of the chromophores has been studied by recording the intensity of the frequency doubled light, generated by a poled sample, with increasing temperature. As expected, photocrosslinking leads to NLO materials with highly stable chromophore orientation.

ISSN:1022-1352    

DOI:10.1002/macp.1995.021960108

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe coupling of dichloromethylphenylsilane (1) with chlorotrimethylsilane (2) by lithium is considered for the synthesis of low‐molecular‐weight organosilane polymers3and for the preparation of heptamethylphenyl‐2‐trisilane (3a) and octamethyldiphenyl‐2,3‐tetrasilane(3b). Size‐exclusion chromatography, ultraviolet and infrared spectroscopies and nuclear magnetic resonance (1H,13C and29Si NMR) analyses of the crude product3were performed and compared with those of3aand3b. According to the spectroscopic characteristics of heptamethyltetrakis(trimethylsilyl)‐3,4,5,6‐cyclohex‐1‐enyl‐2‐trisilane(4), and the observed silylation of the trisilane3awhen it is submitted to the action of a (CH3)3SiCl/Li/tetrahydrofuran system, the silylation of the phenyl ring during the reductive condensation of the chlorosilanes is supported by NMR identific

ISSN:1022-1352    

DOI:10.1002/macp.1995.021960109

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe synthesis ofN‐acryloyl‐L‐valine (NAVAL) andN‐acryloyl‐L‐phenylalanine (NAPHE) have been carried out from L‐valine and L‐phenylalanine. The chiral compounds have been characterized by1H and13C nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy and polarimetry. The copolymerization of NAVAL salt, (NAVAL Na, monomer A) or NAPHE salt (NAPHENa, monomer A′) with acrylamide (AM, monomer B) has been investigated using K2S2O8as initiator, over a range of the feed compositions for NAVALNa (or NAPHENa) from 10 to 100 mol‐%. The compositions of copolymers have been systematically assessed through13C NMR. The reactivity ratios for the couple A, B were determined asrA= 0,67,rB= 0,91 and for the couple A′, B they have been evaluated to be:rA′= 0,40,rB= 0,91. The azeotropic composition is located at 21 mol‐% for the couple A, B and at 13 mol‐% for the couple A′, B. Drag reduction effects are

ISSN:1022-1352    

DOI:10.1002/macp.1995.021960110

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY