Thermally cleavable multiarm and miktoarm star polymers via Diels-Alder / retro Diels-Alder strategy

Abstract

Diels-Alder reaction is a well known [4+2] cycloaddition reaction between a diene and a dienophile. The fact that Diels-Alder reaction takes place even at room temperature without use of any other reagents and reverse reaction, retro Diels-Alder, occurs at elevated temperature makes this reaction a widely used method in synthesis of macromolecular chemistry. By using the thermoreversible feature of this reaction, thermally cleavable multiarm and miktoarm star polymers are synthesized. Symmetrical and unsymmetrical multiarm star polymers containing thermoreversible furan-maleimide core have been synthesized by utilization of atom transfer radical polymerization (ATRP) of MMA using corresponding multiarm macroinitiators. Peripheries of dendritic macroinitiators contain multiple halogen groups which yield star shape upon polymerizaion. Thermal cleavge of the multiarm star polymers are achieved by the retro Diels-Alder reaction of furan-maleimide core at elavated temperature with the presence of maleimide group scavenger. The second study involves the synthesis of thermally cleavable linear and star shaped miktoarm polymers based on unsymmetrically core functionalized initiators via Atom Transfer Radical Polymerization (ATRP) and Ring Opening Polymerization (ROP). Dendrons bearing maleimide groups in their core are furnished with initiators at end of their arms for polymerization of several methacrylates and lactides. Thermal cleavage of miktoarm polymers are achieved by the retro Diels-Alder reaction of furanmaleimide core at elavated temperature with the presence of maleimide group scavenger.