Application of fluorescent polythiophenes and related conjugated polymers as a platform for highly sensitive chemo- and biodetection can benefit from the possibility to effectively control their conformation and conjugation length by applying external stimuli. Temperature call be used Lis such a stimulus if a substantial effect call be achieved in a relatively narrow temperature range. To investigate the temperature-induced conformational switching, a series of polythiophenes with different degree of regioregularity were prepared and functionalized by grafting temperature-responsive poly(N-isopropylacrylamide) (PNIPAm) side chains to their conjugated backbones. These highly water-soluble fluorescent brush-type copolymers featured almost complete lack of intermolecular electronic interactions even in aggregated state owing to remarkably insulating properties of the PNIPAm grafts. Therefore, these grafted copolymers provided an opportunity to study the effects originating from the conformational switching within isolated individual polymer chain, without any impact from interchain interactions. The unique property of PNIPAm-hydrophilic extended coil to hydrophobic collapsed globule phase transition occurring in a very narrow temperature interval-resulted in reversible temperature-induced twisting of the polythiophene conjugated backbone, which was accompanied by pronounced spectroscopic changes. Remarkably, both the extent and appearance of the conformational twisting were found to be strongly dependent on regioregularity of the polythiophene backbone. Low regioregularity copolymer showed Much smaller magnitude of the conformational twisting yielding only subtle spectral changes which Occurred as a threshold process ill it narrow temperature interval. In contrast, higher regioregularity copolymers demonstrated large conformational twisting and substantial spectral changes occurring continuously ill a broad temperature interval. A qualitative explanation of this phenomenon was proposed based On the results of spectroscopic, thermal, and light-scattering experiments.