摘要:

AbstractChitosan was crosslinked to varying extents with bis(vinylsulfonyl)arenes as crosslinking agents in homogeneous solution. The effect of reaction conditions on the onset of gelation was investigated. The rate of gelation was shown to depend on the chitosan concentration and the structure of the crosslinking agent used. The degree of crosslinking and content of the remaining pendant double were evaluated. The obtained cnitosan gels swell both in organic solvents and in acidic aqueous solutions.

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940701

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe structure and miscibility of polyimide PBPI‐E/PTI‐E blends were studied by wide‐ and small‐angle X‐ray scattering and dynamic mechanical analysis, where PBPI‐E is a biphenyldianhydride‐based polyimide, and PTI‐E is a polyimide from 4,4′‐thiodiphthalic anhydride and 4,4′‐oxydianiline. The results obtained show that there exists a paracrystalline structure in the blends with high content of PBPI‐E, but this does not affect the miscibility of the blends. The blends are miscible over the entire composition range, since only oneTgwas observed for each blend. Meanwhile, the segregation of PTI‐E during crystallization of PBPI‐E i

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940702

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe Hofmann modification of polyacrylamide to yield vinylamine homo‐ or copolymers was reinvestigated in order to determine the real scope of a procedure of great potential interest in polymer chemistry. The conditions of the treatment by sodium hypochlorite followed by concentrated sodium hydroxide at low temperature (0°C) were adjusted to avoid or to limit side‐reactions between pendant reactive groups. A broad range of initial mole ratioaof sodium hypochlorite per initial amide function (0,05

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940703

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractAmphiphilic surface active vinyl monomers (alkyl‐2‐methacryloyloxyethyldimethylammonium bromides) with a long alkyl chain (C8/, C12, C14, C16, and C18) were investigated with respect to their polymerization behavior in the absence of an initiator. These monomers polymerized spontaneously in water, through a free‐radical mechanism, except for the ‘C8monomer’. In the polymerization of the ‘C16monomer’, the polymer yield depended on polymerization temperature, and the intrinsic viscosity of the resulting polymer varied with the initial concentration of the monomer just like in ordinary polymerization. The ‘C18monomer’, having low reactivity, became highly polymerizable upon mixing with a quaternary surfactant (dodecyl‐2‐isobutyryl‐oxyethyldimethylammonium bromide) in a particular mole ratio, owing to a change in the monomer aggregation state. In benzene, all of the quaternary methacrylates polymerized spontaneously, too. It is obvious that formation of monomer aggregates, micelles or reverse micelles is essential for the spontaneous polymerization. The spontaneous polymerization of other quaternary monomers, having a hexadecyl group and a polymerzable acryloyl, acrylamido, or methacrylamido moiety, did also occur, yet with lower rate than in c

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940704

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

Abstract1,1,3‐Trimethyl‐3‐[4‐(4‐fluorobenzoyl)phenyl]‐6‐(4‐fluorobenzoyl)indan (5a) and the isomer5bwere synthesized by Friedel‐Crafts acylation of 1,1,3‐trimethyl‐3‐phenylindan with 4‐fluorobenzoyl chloride. This reaction yields a mixture of two isomer. The pure isomer as well as the isomer mixture were employed in the synthesis of poly(ether‐ketone)s via nucleophilic displacement of activated aromatic halogens by different diphenols. The influence of the indan structure element on the polymer properties such as glass transition temperature, crystallinity, solubility, and thermal

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940705

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractN‐(2,4,6‐Tribromophenyi)maleimide (TBPMI) was copolymerized with methyl acrylate (MA) or methyl methacrylate (MMA) in toluene solution using 2,2′‐azoisobutyronitrile as free‐radical initiation. The copolymerization reactivity ratios were found to be for the system TBPMI/MAr1= 0,095 ± 0,045 (TBPMI) andr2= 2,17 ± 0,142 (MA) and for the system TBPMI/MMAr1= 0,037 ± 0,042 (TBPMI) andr2= 4,32 ± 0,230 (MMA);Qandevalues were also calculated. The initial rate of copolymerization,Rp, for TBPMI/MA sharply decreases as the content of TBPMI in the monomer mixture increases but the composition of the feed does not have a strong influence onRpfor the TBPMI/MMA copolymerization system. The course of copolymerization to high conversion is characterized by an increase of conversion up to a mole fraction of TBPMI of 0,7 in the monomer mixture, when MA was used as the comonomer. An opposite behaviour was found with MMA. Its copolymers show a considerable increase of thermal stability as well as of the glass transition temperatures with increasing

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940706

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe interactions of the hydrobromides of (R)‐ and (S)‐alanine‐N‐methylanilides (1) with 24‐, 27‐ and 36‐membered ring pseudopeptides (H‐24, H‐27andH‐36, respectively) derived from glycine and (2S,3′S)‐4‐methyl‐2‐(2′‐oxo‐3′‐isobutyl‐1′‐piperazinyl)pentanoic acid were studied by means of1H and13C NMR measurements in CDCl3. It was found from these results thatH‐24andH‐27distinguished (R)‐ and (S)‐isomers of1, whileH‐36did not entirely. Moreover, the enantioface‐differentiating abilities of these cyclic peptides were investigated by means of1H NMR measurements in CDCI3using (R)‐ and (S)‐1‐phenylethylammonium and (R)‐ and (S)‐p‐methoxy‐1‐phenylethylammonium bromides as the substrates, showing that the enantio‐selectivity ofH‐36is superior to those ofH‐24andH‐27. Also, the chiral recognition ability ofH‐24for the hydrochlorides of (R)‐ and (S)‐alanine (Ala), ‐leucine (Leu), ‐methionine (Met), ‐phenylalanine (Phe), ‐proline (Pro) and ‐valine (Val) methyl esters were examined by1H and13C NMR measurement

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940707

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA series of high‐molecular‐weight amorphous and semicrystalline poly(aryl ether bisketone)s were prepared from bisphenols and 3,4′‐bis(4‐fluorobenzoyl)biphenyl via nucleophilic aromatic substitution reactions. Model compound studies were carried out with several substituted monohydric phenols, 3,4′‐bis(4‐fluorobenzoyl)biphenyl and 3,4′‐bis(4‐Chlorobenzoyl)biphenyl. The dihalo‐substituted aromatic ketones were synthesized by the reaction of 3,4′‐biphenyldicarboxylic acid with thionyl chloride, followed by Friedel‐Crafts acylation with the appropriate aryl halide. The required dicarboxylic acid was prepared starting from 4‐bromotoluene and 3‐methylcyclohexanone. Potassium carbonate mediated reaction of the monomers in dimethylacetamide or diphenyl sulfone gave high‐molecular‐weight polymers in excellent yield. The glass transition temperatures of the polymers are in the 170 to 190°C range. In addition, the polymers exhibit excellent thermal stability, as evidenced by both dynamic and isothermal thermogravimetric analysis, and aff

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940708

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractTheviscosity distributionof a polymer sample can be obtained by using an on‐line viscometer as a detector in size‐exclusion chromatography. This newly definedviscosity distributionis closely related to the molecular weight distribution and expresses weight fraction times intrinsic viscosity of speciesias a function of the corresponding molecular weight times intrinsic viscosity (wi[ηi] vs.Mi[ηi]). The intrinsic viscosity ([η]) and number‐average molecular weight (M̄n) can be obtained directly from aviscosity distribution. If the Mark‐Houwink exponentais known (or approximately known) for non‐homogeneous polymer the M̄w/M̄ncan be estimated from theviscosity distributionwhen the molecular weight distribution is approximated with a known distribution function. These estimates are independent of any other detector and are valid even for non‐homogeneous polymer samples. The relation between the moments of theviscosity distributionand the M̄w/M̄nis presented for two widely used distribution functions, the Log‐Normal and the Generalized Exponential Distributions. Polymer characterization based on theviscosity distributionis shown to be a robust technique. It is particularly attractive in characterizing non‐homogeneous polymers since it is solely obtained

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940709

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractIn order to obtain the correct calibration of molecular‐weight sensitive detectors (such as on‐line viscometers or light scattering detectors) in size‐exclusion chromatography, it is necessary to account for the (molecular) non‐uniformity of the calibration standards. This is true even in the case of the narrow molecular weight distribution standards typically commercially available for calibration. Methods of taking this non‐uniformity into consideration are presented. For a multi‐detector size‐exclusion chromatography system calibrated in this way, independent calibration curves can be established for each detector. Thus, at a given hydrodynamic volume, corresponding signals from the different detectors can be obtained. This eliminates the need to estimate additional parameters such as interdetector volumes or lag times for matching signals from different detectors. The practicability of this approach in the analysis of (molecularly) non‐uniform polymers is demonstrated by combining on‐line viscometer and concentration signals (to obtain intrinsic viscosity versus molecular weight information) for two different polymers, viz. polystyrene and poly(methyl methacrylate). The resultant intrinsic viscosity versus molecular weight data is then compared to that predicted fr

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940710

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY