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The Influence of Functional Groups on the Phase Separation and Molecular Dynamics of Poly(Methyl-Methacrylate) and Polyurethane Mixtures

The phase separation in polymer mixtures of segmented polyurethane (PU) and polymethacrylate copolymer (PM) was studied by electron spin resonance (ESR) in the temperature range from 170 K-393 K. The interaction between the two polymer components was promoted by introducing functional groups: carboxylic groups in the hard segments of PU component and tertiary amine groups in the PM component. The influence of functional group content on the phase behaviour of 1:1 by weight polymer mixtures was recorded using the nitroxyl spin label and spin probe method. The composed ESR spectra of nitroxyl radical covalently attached to the PM chains have shown that the part of PM chains are incorporated in the soft segment domains of PU. PM chains partitioned in the fast or soft phase are below the glass transition temperatures of the pure PM copolymer. Analysis of the spectra suggest an increase of the polymer-polymer interaction by augmenting the content of functional groups. The results obtained for the spin probe reveal that the two phase spectra of PU component are sensitive to the presence of PM chains. Spin probe indicates dynamically different molecular environments depending on the interaction between the functional groups and the fluctuation of free volume at the interphase. The influence of spin probe size and polarity in the study of free volume generation and dynamic behaviour of polymer mixtures is analysed. The results are compared with the DSC measurements.

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