ISSN:0323-7648    

DOI:10.1002/actp.1996.010470801

出版商:Akademie Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractHigh molecular weight and low charge density ampholytic terpolymers based on acrylamide (AM), as a neutral monomer, and sodium 2‐(acrylamido)‐2‐methylpropanesulfonate (NaAMPS) and [2‐(methacryloyloxy)ethyl]trimethylammonium chloride (MADQUAT) as charged monomers have been prepared by a microemulsion polymerization technique. An optimization of the process for the selection of the different components of the microemulsion has been achieved by applying criteria based on the hydrophile‐lipophile balance (HLB) and cohesive energy ratio concepts. Composition‐conversion curves were determined for samples containing different monomer feeds. The drifts observed in the terpolymer compositions with conversion were compared to those calculated from the reactivity ratios determined in binary copolymerizations performed in solution and in microemulsion. The results show that the reactivity of the monomers in ternary systems depends on the ionic strength, i.e. on the monomer feed

ISSN:0323-7648    

DOI:10.1002/actp.1996.010470802

出版商:Akademie Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractA study of the low‐angle region of the static structure factorS(q)(q = (4π/λ) sin(θ/2); θ: scattering angle, λ: wavelength of the radiation in the medium) of a concentrated (44 wt.%) poly(methyl‐methacrylate) (PMMA) latex by turbidimetry is presented. It is demonstrated thatS(0), i.e., the structure factor extrapolated to vanishing scattering angle can be obtained in excellent accuracy up to the highest concentrations. SinceS(0)reflects the balance between long‐range attractive and short‐range repulsive forces between the latex particles, this quantity can be used to assess the stability of the latex against flocculation. Special attention has been paid to the influence of polydispersity onS(0). The analysis ofS(q)in the vicinity ofq= 0 for the system under consideration indicates the absence of attractive forces between t

ISSN:0323-7648    

DOI:10.1002/actp.1996.010470803

出版商:Akademie Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractSilver cluster formation in bulk block copolymer films (static‐cast) and in thin films (microtomed or spin‐coated) was investigated by transmission electron microscopy. In all cases, the silver clusters were formed predominantly within the original silver‐containing microdomains. A greater degree of control of cluster formation and a narrower cluster size distribution were achieved in the thin films of block copolymers. The interfaces between domains of the heterogeneous copolymers and the free interfaces of the thin film specimens all played an important role in nucleation and growth of clu

ISSN:0323-7648    

DOI:10.1002/actp.1996.010470804

出版商:Akademie Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractOxygen‐organoslov lignin (namely oxygen‐acetone) was introduced as a macromonomer into polyesterification systems including diacid chlorides and, optionally, oligoethyleneoxide glycols. It was concluded that the incomplete participation of phenolic hydroxy groups of lignin in these polycondensation reactions could lead to poor crosslinking as shown by the partial solubility of the final polyesters in polar solvents. This paper presents the synthesis, characterization and some properties of these materi

ISSN:0323-7648    

DOI:10.1002/actp.1996.010470805

出版商:Akademie Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractA convergent synthesis of polymerizable dendrimers consisting of one methacrylic function combined with an alkylene spacer and several condensed L‐aspartic acid components is described. The highly functionalized monomers were prepared fromN‐methacryloyl amino undecanoic acid (9) via condensation with free amino groups of L‐aspartic acid dimethyl ester (2), α, β‐bis‐(L‐dimethoxyaspartyl)‐L‐aspartic acid hydrobromide (4) and α, β‐bis‐(L‐aspartyl‐α, β‐bis‐(L‐dimethoxyaspartyl))‐L‐aspartic acid hydrobromide (6). The number of ester groups increased from 2 to 4 and 8, up to 16, depending on the dendritic generation of the condensed amino acids. The monomers were homopolymerized and copolymerized with s

ISSN:0323-7648    

DOI:10.1002/actp.1996.010470806

出版商:Akademie Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractEnzymatic ring‐opening polymerization of a 16‐membered lactone, 15‐pentadecanolide (PDL), has been carried out in bulk using various lipases of different origin as catalyst. The polymerization withPseudomonas fluorescenslipase (lipase PF) catalyst afforded the corresponding polyester in high yields. The rate of the polymerization catalyzed by lipase PF at a temperature lower than 45°C was very small, whereas the polymerization at higher polymerization temperature (≥60°C) proceeded much faster. Lipase derived fromPseudomonas cepaciawas also active for the polymerization of PDL. The polymerization catalyzed byCandida cylindracealipase at high temperature (75°C) afforded the polymer with molecular weight up to 2.0 x 104. The polymerization behavior of PDL through lipase catalysis has been compared with that of ε‐caprolactone (ε‐CL). PDL showed an enzymatically higher polymerizability than ε‐CL, despite the smaller ring‐strain of PDL, which is due to the stronger recognition of PDL by lipase. Enzymatic copolymerization of PDL with other lactones using lipase PF catalyst produced copolymers with molecular weight of several thousands. From13C NMR analysis, the diad sequence distribu

ISSN:0323-7648    

DOI:10.1002/actp.1996.010470807

出版商:Akademie Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractA prominent reduction of the layer thickness,d1, in the Sm A and Sm B phases with increasing temperature has been observed for a series of side chain polymers. The maximum decrease ind1value for one of the copolymers is ∼7Å; i.e. 15% of its total value. The influence of the chemical structure of the main chain and side groups on the effect has been studied. Models have been proposed for packing of mesogenic side groups at different temperatur

ISSN:0323-7648    

DOI:10.1002/actp.1996.010470808

出版商:Akademie Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractPartially stereoregular poly(propylene oxide) (PPO) samples synthesized using Pruitt‐Bagett catalysts (PBC) were fractionated at 40°C and 70°C from acetonitrile solution by adding small portions of water. The formed polymer‐rich phases were clear liquids except the first three fractions obtained at 40°C; those were solids. The fractions were characterized with their viscosity average molecular masses and melting points. Results showed that the procedure described in the present report fractionates partially stereoregular PPO on the basis of molecular weight, independent of their tac

ISSN:0323-7648    

DOI:10.1002/actp.1996.010470809

出版商:Akademie Verlag GmbH    

年代:1996

数据来源: WILEY