Abstract: Provided is a novel polystyrene-based polyampholyte having upper critical solution temperature (UCST)-type thermoresponsiveness and a method for producing the same. When monomers having halogenated vinylbenzyl trialkyl ammonium and p-styrenesulfonate as main components are radically polymerized in an aqueous solvent, a polyampholyte having an upper critical solution temperature is produced by optimizing the mole ratio between cationic groups and anionic groups and the amount of a radical initiator and a chain transfer agent to be added to thereby control the copolymer composition and the molecular weight.

Abstract: A photosensitive resin realizes formation of a pattern having a good shape, without introducing poor compatibility between an acid generator and a photoresist primary-component polymer having an acid-dissociable group, and a photosensitive composition containing the photosensitive resin. The photosensitive resin includes a repeating unit represented by formula (1): (wherein R1 represents a C2-C9 linear or branched divalent hydrocarbon group; each of R2 to R5 represents a hydrogen atom or a C1-C3 linear or branched hydrocarbon group; each of R6 and R7 represents an organic group, wherein R6 and R7 may together form a divalent organic group; and X?represents an anion); at least one of a repeating unit represented by formula (2): (wherein R8 represents a C2-C9 linear or branched hydrocarbon group) and a repeating unit represented by formula (3): a repeating unit represented by formula (4): optionally, a repeating unit represented by formula (5).

Abstract: To provide a photosensitive resin which realizes formation of a pattern having a good shape, without involving a problem in terms of poor compatibility between an acid generator and a photoresist primary-component polymer having an acid dissociable group, and a photosensitive composition containing the photosensitive resin.