Degradable 3-Arm Polymers Using Acid-Cleavable Chain Transfer Agent

Reversible addition−fragmentation chain-transfer (RAFT) polymerization is recognized as one of the efficient controlled radical polymerization techniques. It is a straightforward yet powerful approach to obtain structurally well-defined polymers. Herein, we introduce multifunctional RAFT agent incorporating three acid-cleavable acetal group that can be degraded by acid to achieve intricate polymer architectures with a degradable characteristic. Using the designed RAFT agent, we synthesized 3-arm poly(methyl methacrylate) that can be broken down by acid into three linear chains, leading to altered physicochemical properties due to the reduction in molecular weight. This design was further extended to chemically amplified resist systems, in which the patternability with lower acid concentration became more challenging in high-resolution photolithography. Upon the illumination of light with specific wavelength, acid-catalyzed deprotection reaction undergoes, resulting in the chemical transformation and subsequent increase of solubility in a specific solvent. Compared to its linear terpolymer, the branched form exhibited enhanced capability for modulation of dissolution behavior, due to significant reduction of molecular weight, which is beneficial for the improvement of sensitivity in photoresist materials.