Volume 55 Issue 7, July 2023

We fabricated polymer brushes using a novel concept, which involves block copolymer segregation from the polymer region at the water interface. The resulting polymer brush is called a dynamic polymer brush because block copolymer segregation is a dynamic process that occurs at room temperature and is activated through contact with water. Dynamic polymer brushes undergo self-organization in the processes of self-assembly and self-healing (if destroyed). The concept and physical characteristics of dynamic polymer brushes are discussed in this review.

Nucleobase modification of acyclic XNA oligomers achieved functionalization for use as a novel fluorescent probe and photoswitching system. A linear probe, composed of serinol nucleic acid (SNA) and 5-perylenylethynyl uracil residues, enabled quantitative detection of target RNA through a visually observable change in fluorescent color and intensity. A photoresponsive SNA with two 8-pyrenylvinyl adenine (^PVA) residues established photocontrol of SNA/RNA duplex formation and dissociation. Using a combination of 8-naphthylvinyl adenine (^NVA) and ^PVA demonstrated orthogonal photocontrol system. Thus, nucleobase modifications further expand the utility of acyclic XNA in bionanotechnology.

Sustainable and 100% biobased plastics, polyamide 11 (PA11), derived from nonedible plants are mixed with polypropylene (PP) and a reactive compatibilizer in a twin-screw extruder. It is found that PP/PA11 bioalloys exhibited surprisingly good impact strength without losing flexural modulus only when the morphology of the PP/PA11 bioalloys was well controlled at nano-meter level, such as “nano-salami” structure. This leads to overcome a past and traditional issues in biobased plastics, resulting in applying for automobile plastic parts. This technology would contribute to realizing “carbon neutrality”.

Time-resolved FTIR was used to study the crystallization kinetics of syndiotactic polystyrene. Isothermal crystallization from the melt by cooling and from the glass by heating was used to determine the temperature (T_c) dependence of the crystallization rate (k). Based on the derived k and the crystal growth rates (G) obtained from OM and depolarized light scattering, the density of primary nucleation was readily calculated. The magnitudes of the nucleation densities in the cold-crystallized samples were ~5−6 orders higher than those of the melt-crystallized samples despite the similar k values.

The melting temperature of the isothermally crystallized poly(trimethylene terephthalate) (PTT) lamellar stack structure was determined by X-ray measurements. The equilibrium melting temperature of PTT was determined to be 290.5 °C from the relationship between the melting temperature and the lamellar thickness. The temperature dependence of the lamellar thickness below T_c = 173.7 °C suggested crystallization through a mesophase. The temperature dependence of the growth rate was explained by secondary nucleation theory over a wide crystallization temperature range.

Catechol-modified alginates (AlgDAs) with various catechol contents were synthesized and examined as adhesive materials. AlgDA exhibited high adhesive strength with mica and moderate adhesive strength with polymer resins, although this adhesiveness was not observed for sodium alginate. AlgDA with a relatively low catechol content exhibited relatively high adhesive strength, unlike other catechol-modified polymer adhesives. AlgDA residues were successfully removed from the used substrates by a simple water washing process. AlgDA is promising as a biobased adhesive material that contributes to a sustainable society.

Distannylated dithiazologermole and germaindacenodithiazole were copolymerized with dibrominated benzothiadiazole and di(thiazolyl)benzothiadiazole to produce four new donor-acceptor conjugated copolymers. The optical, electrochemical, and thermal properties of the copolymers were characterized. DFT calculations revealed that these thiazole-containing copolymers possessed lower HOMOs and LUMOs than those of thiophene-based congeners, in accordance with the experimental results. The intramolecular noncovalent S‒N and N‒H bond interactions and the effects of the bridging atom (C or Ge) on the HOMO and LUMO energy levels were also suggested by the DFT calculations.