Supramolecularly Designed Thermoresponsive Polymers in Different Polymer Backbones

Self-Assembly of Chemically Programmed Amphiphiles into Aqueous Nanotubes with a Lipophilic Lumen

The creation of complex hollow nanostructures with precise control over size and shape represents a great challenge in supramolecular soft materials. Here, we have further developed a bioinspired methodology for the formation of aqueous nanotubes of well-defined dimensions and pore coating through the self-assembly of amphiphiles that are chemically programmed with complementary nucleobases. These nanotubes are endowed with a hydrophobic lumen, whose diameter can be expanded as a function of the monomer length, in which apolar dyes can be efficiently encapsulated.

Rationale Design for Anchoring Pendant Groups of Zwitterionic Polymeric Medical Coatings

A biocompatible and antifouling polymeric medical coating was developed through rational design for anchoring pendant groups for the modification of stainless steel. Zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) was copolymerized individually with three anchoring monomers of carboxyl acrylamides with different alkyl spacers, including acryloylglycine (2-AE), 6-acrylamidohexanoic acid (6-AH), and 11-acrylamidoundecanoic acid (11-AU). The carboxylic acid groups are responsible for the stable grafting of copolymers onto stainless steel via a coordinative interaction with metal oxides. Due to hydrophobic interaction and hydrogen bonding, the anchoring monomers enable the formation of self-assembling structures in solution and at a metallic interface, which can play an important role in the thin film formation and functionality of the coatings. Therefore, surface characterizations of anchoring monomers on stainless steel were conducted to analyze the packing density and strength of the intermolecular hydrogen bonds. The corresponding copolymers were synthesized, and their aggregate structures were assessed, showing micelle aggregation for copolymers with higher hydrophobic compositions. The synergistic effects of inter/intramolecular interactions and hydrophobicity of the anchoring monomers result in the diversity of the thickness, surface coverage, wettability, and friction of the polymeric coatings on stainless steel. More importantly, the antifouling properties of the coatings against bacteria and proteins were strongly correlated to thin film formation. Ultimately, the key lies in deciphering the molecular structure of the anchoring pendants in thin film formation and assessing the effectiveness of the coatings, which led to the development of medical coatings through the graft-onto approach.

Synthesis and cationic polymerization of halogen bonding vinyl ether monomers

Halogen bonding is rapidly becoming recognized as a viable and useful intermolecular interaction in supramolecular chemistry. While various monomers amenable to radical polymerization methods containing halogen bonding donors have been developed, this study aims to expand the type of monomers that incorporate this intermolecular interaction to facilitate use of cationic polymerization by developing three novel vinyl ether monomers containing halogen bonding donor moieties: 2,3,5,6-tetrafluoro-4-iodophenoxyethyl vinyl ether (C2I), 2,3,5,6-tetrafluoro-4-iodophenoxybutyl vinyl ether (C4I), and 2-(2,3,5,6-tetrafluoro-4-iodophenoxyethoxy)ethyl vinyl ether (O3I). Well controlled cationic polymerization is achievable through the use of a proton trap, 2,6-di-tert-butylpyridine. The use of SnCl₄ as a co-Lewis acid was found to accelerate the reaction. Between the three monomers, the difference in the chain length is shown to influence the reaction rate, with the longest chain demonstrating the fastest polymerization. Initial studies of the halogen bonding ability shows that halogen bonding exists for all three monomers but is most pronounced in C4I. The polymerized vinyl ethers also exhibit halogen bonding. Due to the ease of synthesis and polymerization, these are promising new monomers to increase functionality available for polymers synthesized using cationic polymerization.

Three novel vinyl ether monomers containing halogen bonding moieties were synthesized, polymerized via cationic polymerization and exhibited clear halogen bonding.

Thermoresponsive properties of polymer hydrogels induced by copolymerization of hydrophilic and hydrophobic monomers: comprehensive study of monomer sequence and water affinity

In order to raise the possibility of the practical use of thermoresponsive hydrogels in various fields, it is imperative to achieve on-demand control of responsive behavior especially by using a simple synthetic method with common monomers. To this end, we synthesized various hydrophilic/hydrophobic copolymer hydrogels from common acrylamide derivatives and acrylate monomers via free radical copolymerization, and examined the correlation between the structure and the swelling properties of the obtained gels, specifically from the viewpoint of the monomer sequence in the network chains and the affinity to water molecules. The obtained gels with a hydrophobic acrylamide monomer were shown to exhibit a sharp volume change in water upon heating at suitable monomer compositions. In contrast, the gels consisting of a hydrophobic acrylate monomer only decreased the swelling degree with no significant thermoresponsive volume change. The formation of a local amphiphilic structure without a long hydrophobic sequence is critical for achieving sharp thermoresponsiveness. Moreover, the water affinity was drastically changed at a sharp volume transition with the copolymer gels of a hydrophobic acrylamide. This transition was most likely driven by an entropic factor because of the strong contribution of the hydration/dehydration of the network chains. The comparison of the temperature-responsive behavior of the gels with that of the corresponding linear copolymers demonstrated that the crosslinking structure made significant hydrophobic contribution to the responsive behavior.

Exploring the tubular self-assembly landscape of dinucleobase amphiphiles in water

The tubular aqueous assembly of dinucleobase amphiphilic monomers endowed with anionic, neutral or cationic groups is investigated under diverse conditions.