Self-Activation of Poly(methylenelactide) through
Neighboring-Group Effects: A Sophisticated Type of Reactive Polymer
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Abstract
The
present work reports on a reinvestigation of a radical polymerizable
lactide derivative since the polymerization properties were only poorly
studied in the first publication in 1969. The optically active methylenelactide
was polymerized by free radical polymerization in solution using AIBN
as an initiator and resulted in isotactic-biased atactic optically
active poly(methylenelactide) according to <sup>1</sup>H NMR and <sup>13</sup>C NMR spectroscopies and specific rotation angle measurements
[α]<sup>20</sup><sub>D</sub> = −38.5 ± 0.5°.
The molecular weights range between 4 × 10<sup>4</sup> and 1
× 10<sup>5</sup> g mol<sup>–1</sup> with dispersities
of ca. <i>D</i> = 2.5 and a detected glass transition temperature
of 244 °C. IR spectra of the polymers indicate different ester
reactivities (ν<sub>a</sub> = 1779 cm<sup>–1</sup>, ν<sub>b</sub> = 1755 cm<sup>–1</sup>) that can be referred to as
neighboring-group effects. These highly activated esters react readily
with nucleophiles in polymer analogous reactions. Thus, the aminolysis
of poly(methylenelactide) was performed under mild conditions with
varied amines. In the case of aminolysis with tetrahydrofurfurylamine,
a nonstable cloud point in water was observed
