Interfacial tensions γ were measured for mixtures of poly(methylphenylsiloxane) (4 kg/mol) and poly(dimethylsiloxane) (24 kg/mol) in the absence and in the presence of small amounts of the random copolymer poly(dimethylsiloxane-ran-methylphenylsiloxane) (89 mol-% of dimethylsiloxane units, 28 kg/mol) from 25 to 110°C. Approximately 1 wt.-% of the copolymer additive suffices to reduce γ from ca. 2.2 to 1.6 mN/m. The time dependence of the apparent γ value in the course of the attainment of equilibria also indicates surface acivity. The hypothesis is formulated that the efficiency of the random copolymer for a reduction of γ is bound to the condition that it is only sparingly soluble in both blend components.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis, glass transition behavior, and solution characterization of poly[(aryloxy)thionylphosphazenes] with halogen substituents at sulfurYizeng Ni, Andreas Stammer, Mong Liang, Jason Massey, G. Julius Vancso, and Ian MannersCite this: Macromolecules 1992, 25, 26, 7119–7125Publication Date (Print):December 1, 1992Publication History Published online1 May 2002Published inissue 1 December 1992https://pubs.acs.org/doi/10.1021/ma00052a008https://doi.org/10.1021/ma00052a008research-articleACS PublicationsRequest reuse permissionsArticle Views146Altmetric-Citations44LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Abstract Continuous polymer fractionation (CPF) — a new large‐scale method — was applied to the technical poly(methyl vinyl ether) (PVME) using toluence as solvent and petroleum ether as non‐solvent. Two different devices served as fractionation apparatus, namely a column packed with glass beads and a set of mixer‐settler extractors. Advantages and draw‐backs of these devices are discussed. The experiments yielded numerous PVME fractions, varying in molar mass from 22 to 87 kg/mol and in molecular non‐uniformity U = ( M¯ w / M̄ n ) – 1 from 0,25 to 0,41 according to gel‐permeation chromatography as compared with ca. U = 1,30 for the starting material. The following Kuhn‐Mark‐Houwink relation was established for PVME in ethyl methyl ketone at 30°C: [η]/(mL/g) = 2,6 . 10 −3 M̄ 0,86 .
Abstract Cloud point curves were measured turbidimetrically for blends (upper critical solution temperatures; UCSTs) of poly(ethylmethylsiloxane) (PEMS) and four different samples of poly(dimethylsiloxane) (PDMS); the weight average molar masses in kg/mol are 31.2 for PEMS and 10.4, 15.5, 18.1 and 24.0 for PDMS; all components have polydispersity indices D (= M̄ w /M̄ n ) within the range from 1.82 to 2.67. Corresponding calculations on the basis of the Flory‐Huggins theory (three adjustable parameters) account for the poly‐dispersity; molecular weight distributions are represented by the generalized Schulz‐Flory equation. Calculated cloud point curves agree very well with those measured, if individual sets of parameters are admitted for each of the different mixtures. Even for an identical set of parameters the maximum deviations remain moderate. Realistic model calculations concerning the influences of D on cloud points and on critical points were performed with this set of parameters. For the present (only slightly endothermal) system, the precipitation threshold increases from 318 to 558.6 K as D PEMS is raised from 1.87 to 4.00, keeping the number average degree of polymerization constant.
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