Association of Stereoregular Poly(methyl methacrylates)

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Abstract
Isotactic and syndiotactic poly(methyl methacrylate) (i-and s-PMMA) form stereocomplexes in suitable solvents. Viscometric and turbidimetric studies of this stereoassociation have led us to divide the solvents into 3 types. Type A solvents are polar solvents which promote stereoassociation, resulting in gelation and precipitation. Type B solvents are nonpolar aromatic solvents, wherein stereoassociation is weaker but still leads to gelation. Type C solvents are very good solvents in which stereoassociation does not occur. It appears that the so-called stereospecific replica polymerization of methyl methacrylate on Stereoregular PMMA as a polymer matrix in the different types of solvents is closely related to the above mentioned tendency of i-and s-PMMA to associate. The replica efficiency of the matrix decreases in the order A > B > C = 0. The stereocomplexes formed in situ during stereospecific replica polymerization were investigated and compared with those obtained by mixing solutions of i-and s-PMMA. It seems that the 1:2 i/s stereo-complex which shows thermal properties quite different from its components, is the most stable one.

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