One‐Step Synthesis of Alkaline‐Soluble Polystyrene Containing Trimethoxysilyl‐ and Boronic Acid‐Moieties as Inorganic, Reactive Pendant Groups for Photosensitive Materials

Abstract It is of great interest in simple preparation of organic–inorganic hybrid thermoset soluble in alkaline developer, intended for photosensitive materials used in the field of semiconductor packaging based on sophisticated molecular design from the viewpoint of performance improvement and cost reduction. Here successful one‐step synthesis of alkaline‐soluble polystyrene with three kinds of pendant groups along the chain; trimethoxysilyl (TMS), boronic acid (BA), and hexafluoroisopropylalcohol (HFA) groups is shown. Solvent composition‐based equilibrium control of reactions involving the inorganic pendant groups (TMS and BA) as well as the hydrogen bonding ability and sterically bulky structure of the HFA group are effective in suppressing cross‐linking reactions during polymerization. The latter is confirmed through DFT calculation and terpolymerization experiments where the effect of the HFA group is compared to other ten kinds of p‐substituted functional groups. The obtained terpolymer is soluble in alkaline developer and forms an insoluble membrane with high heat‐resistance after heat treatment. Furthermore, its photosensitive polymer composition with photochemical acid generator exhibits negative‐type photosensitivity. The organic–inorganic hybrid thermosetting polystyrene is a promising material for semiconductor package applications.