The use of molecular recognition to obtain selective blending in polymer systems

Abstract

A series of copolymers were prepared in which specific hydrogen bonding sites were incorporated that were either the pyrimidine–purine base pairings found in DNA or analogues of these. Copolymers of poly(methylacrylate-stat-maleimide), MA/MI, were blended with samples of copolymers poly(styrene-stat-7-[2-methacryloyloxy] ethyladenine), S/MAAd, and poly(methyl methacrylate-stat-7-[2-methacryloyloxy]ethyladenine), MMA/MAAd, and found to form miscible blends when the composition of the copolymers contained ≥15mol% of the hydrogen bonding units, MI and MAAd. These form triple hydrogen bonded structures and promote stable one phase blend formation.However, it was found that if S/MAAd was blended with copolymers of poly(methylacrylate-stat-vinyl cytosine) the blends were immiscible over the whole range of compositions studies. This was attributed to the fact that cytosine and adenine do not form stable hydrogen bonded combinations in nature and will selectively reject each other as complementary hydrogen bonding pairs. This shows that in principle the use of such units in synthetic polymer systems could allow selective blending and the formation of controlled structures.