Glycolated polythiophenes are of great interest for their use as organic mixed ionic-electronic conductors (OMIECs). In this study, we elucidate the polymerization mechanism for the synthesis of poly(3-((2-(2-methoxyethoxy)ethoxy)methyl)thiophene) (P3MEEMT) using Kumada catalyst transfer polymerization (KCTP). While the use of i-PrMgCl·LiCl (turbo-Grignard) for monomer activation enabled rapid polymerization within 10 min at room temperature, this resulted in lower than expected number-average molecular weight (Mn). We propose that the polymerization proceeds via a radical-mediated pathway, a mechanism not observed for poly(3-hexylthiophene) (P3HT). This was demonstrated by the complete inhibition of the reaction by the radical scavenger TEMPO and the detection of radical species by EPR spectroscopy using DMPO as a spin trap. By introducing MgCl2 after Grignard metathesis, a controlled polymerization was afforded with Mn proportional to the catalyst loading. This work establishes that KCTP of glycolated thiophenes proceeds via a radical-assisted pathway and provides a strategy to control the polymer molecular weight. These findings establish a new principle for controlling polymerizations, where the monomer's physical aggregation state is the key factor in enabling a productive, radical-mediated pathway.
Tailoring the properties of functional polymers through simple structural modifications is a fascinating molecular design strategy. In this work, cyano functionalization of the polymer backbone improved the electrochromic properties of the conjugated porous polymer (CPP) composed of N,N,N′,N′-tetraphenyl-1,4-phenylenediamine (TPPA) and thienylene-vinylene-thienylene (TVT) units. The non-cyanated polymer P(TPPA-TVT) shows multicolor behavior, reversibly switching among orange-yellow, gray-green, and gray. The cyanated polymer P(TPPA-TVTCN) not only exhibits a different neutral-state color but also presents more diverse electrochromic color changes, including brick red, reddish brown, brown, green, and gray-cyan. In addition, the modification of the cyano group improves the cycling stability of the polymer. P(TPPA-TVTCN) retains over 96% of its initial optical contrast after 2000 seconds of repeated redox switching, with a performance significantly superior to that of P(TPPA-TVT). Moreover, P(TPPA-TVTCN) shows better kinetic properties than P(TPPA-TVT) in the near-infrared (NIR) region. At 1380 nm, P(TPPA-TVTCN) displays an optical contrast of 52.6%, response times of 0.76 s and 2.05 s, as well as a coloration efficiency of 231.52 cm2 C−1. The incorporation of the cyano group promotes the formation of a D–A configuration and hence optimizes the optoelectronic properties of the polymer. Besides, the porous structures and extended π-conjugated backbones of the two CPPs help reduce the response time and enhance the cycling stability. Rational polymer design and facile structural adjustment provide an effective way for developing new electrochromic materials.

