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

A series of copolymers were prepared in which specific hydrogen bonding sit es were incorporated that were either the pyrimidine-purine base pairings f ound in DNA or analogues of these. Copolymers of poly(methylacrylate-stat-m aleimide), MA/MI, were blended with samples of copolymers poly(styrene-stat -7-[2-methacryloyloxy] ethyladenine), S/MAAd and poly(methyl methacrylate-s tat-7-[2-methacryloyloxy]ethyladenine), MMA/MAAd, and found to form miscibl e blends when the composition of the copolymers contained greater than or e qual to 15 mol% of the hydrogen bonding units, MT and MAAd These form tripl e hydrogen bonded structures and promote stable one phase blend formation. However, it was found that if S/MAAd was blended with copolymers of poly(me thylacrylate-stat-vinyl cytosine) the blends were immiscible over the whole range of compositions studies. This was attributed to the fact that cytosi ne and adenine do not form stable hydrogen bonded combinations in nature an d will selectively reject each other as complementary hydrogen bonding pair s. This shows that in principle the use of such units in synthetic polymer systems could allow selective blending and the formation of controlled stru ctures. (C) 2001 Elsevier Science Ltd. All rights reserved.