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ContentSEM of the Na 2 CO 3 utilized Preparation of the stock solutions and Schlenk tube Kinetic test for styrene ARGET ATRP with ascorbic acid/Na 2 CO 3 GPC traces of PSs: effect of reaction time and catalyst amount MALLS analyses GPC traces of PSs: effect of dilution with monomer Effect of the EtOAc/EtOH ratio on the polymerization Kinetic investigation Instability of the yellow chromophore Experimental procedure for the isolation of TPMA Reduction of CuCl 2 /TPMA by Na 2 CO 3 in EtOAc/EtOH Linear sweep voltammetry Kinetic comparison between ARGET ATRP with and without ascorbic acid Replacement of Na 2 CO 3 with nitrogen bases Linear sweep voltammetry in S/t-BuOAc/t-BuOH

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Two A‐π‐D‐π‐A thiophene‐based small molecules with a central dithienosilole core and dicyanovinyl (DCV) end groups were synthesized. These compounds differ only by the presence of alkyl and alkylsulfanyl chains, respectively, on the thiophene beta positions. Computational data together with the spectroscopic and electrochemical findings (obtained by means of absorption, steady‐state/time‐resolved emission techniques, and cyclic voltammetry) revealed that both molecules possess low electronic and optical band gaps, broad absorption spectra, and good stability both in p and n‐doping states, which make them suitable for optoelectronic applications. In both compounds, the HOMO–LUMO transition involves an intramolecular charge transfer from the electron‐donor dithienosilole unit to the two terminal electron‐acceptor DCV groups. A marked positive emission solvatochromism was observed for both molecules and was interpreted on the basis of the symmetry breaking in the S1 excited state. The two synthesized compounds were also compared to their shorter precursors and to similar oligothiophenes to understand how the nature of the building block influences the characteristics of the final materials. Furthermore, it was possible to better understand the contribution of the sulfur atom in modulating the optical properties of the small molecules studied.

An anomalous polystyrene gel was obtained during the copper-catalyzed "activators regenerated by electron transfer" "atom transfer radical polymerization" (ARGET ATRP) of styrene at 60-70 °C, using ascorbic acid/Na 2 CO 3 as the reducing system and EtOAc/EtOH as the solvent mixture. The result is remarkable since no branching nor cross-linking reagents were added to the reaction mixture and their formation in situ was excluded. The anomalous PS branching, at the origin of the phenomenon, requires a generic bifunctional initiator and is mechanistically bound to termination reactions between bifunctional macroinitiators. As a matter of fact, the branching/cross-linking phenomenon loses intensity, or even disappears, under reaction conditions that cause the built-up of Cu II or increase the chain polymerization rate. The temperature is also a critical variable since no branching was observed for temperatures higher than 90 °C. We believe that the route toward gelation starts with a controlled chain polymerization of styrene from the bifunctional initiator, soon integrated by a step-growth polymerization due to radical coupling of the terminal units. The progressive decrease in the number of chains and free radicals in the reaction mixture should make more and more probable the intramolecular coupling between the C−Cl ends of the remaining long and entangled chains, producing a polycatenane network.