Nano-fibrils formation of pBTTT via adding alkylthiol into solutions: Control of morphology and crystalline structure

Thermal Stability and Utility of Dienes as Protecting Groups for Acrylamides

Acrylamides are privileged electrophiles used in targeted covalent therapies, often installed at the end of a synthetic sequence due to their reactive nature. Herein, we report several diene-acrylamide adducts with a range of thermal stabilities toward retro-Diels-Alder deprotection of the acrylamide, enabling this masked functionality to be introduced early in a synthetic route and deprotected in a specific temperature range. Through kinetic studies, we identify solvent and structural trends that impact the stability of trimethylsilyl cyclopentadiene (TMS-CP) acrylamide adducts. TMS-CP protected acrylamides were installed on several amine-containing drugs, whose acrylamides were thermally unveiled (T = 160 °C, time ≤ 1 h) in moderate to high yields. We also showcase the potential utility of this protection strategy by improving the yield of a base-promoted SNAr reaction when the acrylamide is masked.

PBTTT-C16 sol-gel transition by rod associations and networking

A low-molecular-weight poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (designated as Lw-pBTTT-C₁₆) in a fair solvent (chlorobenzene, CB) displays peculiar structural, mechanical, and electronic features during sol-gel transition. Using comprehensive (multiscale) dynamic/static analysis schemes, the Lw-pBTTT-C₁₆/CB solution (10 mg mL^-1) is shown to capitalize on rod associations and networking to form a gel, in stark contrast with its high-molecular-weight companion previously reported to form gels through hierarchical colloidal bridging. The present study reveals, however, that the molecular weight of pBTTT-C₁₆ has a subtle impact on the gelation behaviors through the rarely recognized, contrasting supramolecular conformations (rod-like vs. wormlike) of the aggregate clusters fostered in the pristine solution. The ac conductivity nearly doubles as a result of improved (mesoscale) packing of cylindrical aggregates near the gel state as well as enhanced backbone rigidity of the constituting chains. Other distinguishing features include: (1) there is no real crossover of the dynamic moduli (G' and G'') upon increasing the temperature from gel (T = 15 °C) to solution (T = 80 °C) states. (2) The gel is about a hundredfold softer in dynamic modulus, yet more resilient with a fivefold increase in the yield strain. Both viscoelastic features are expected to greatly benefit the gel processability. (3) The coexistent microgels and cylinder (aggregate) bundles form a peculiar gel network that has not been reported previously with polymer or colloidal gels. The overall findings provide new mechanistic insight into the phenomenological effects of molecular weight for the pBTTT-C_n series in solution, sol, gel, and thin film.