Daisuke Matsukuma

Preparation of low-surface-energy poly[2-(perfluorooctyl)ethyl acrylate] microparticles and its application to liquid marble formation.

We demonstrate the successful preparation of stable liquid marbles from various liquids. This is accomplished by using low-surface-energy poly[2-(perfluorooctyl)ethyl acrylate] (PFA-C(8)) as microparticles. The PFA-C(8) microparticles were prepared by the spontaneous self-organized microparticulation of PFA-C(8). The physical properties remained intact in the polymer morphology as confirmed by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) measurements. The extremely low surface energy of PFA-C(8) provides a high solid-liquid spreading coefficient (S(S/L)) value for various combinations of liquids. As a result, liquid marbles were obtained from various liquids, unlike the case with other fluorine polymer particles such as poly(tetrafluoroethylene) (PTFE) and poly(vinilydene fluoride) (PVDF). These results suggest that the technique is widely applicable for preparing novel functional materials.

Self-assembly of poly(ethylene glycol)-block-polypyridine copolymer into micelles and at silica surface: effect of molecular architecture on silica dispersion

We have newly synthesized amphiphilic block copolymers composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic pyridine segments (PEG-b-Py). Chain transfer agent-terminated PEG was subsequently chain-extended with 3-(4-pyridyl)-propyl acrylate to obtain PEG-b-Py by reversible additional-fragmentation chain transfer polymerization. Particularly, the effect of varying molecular weight (Mn) of PEG (Mn = 2,000 and 5,000) and Py in the block copolymers was investigated in terms of critical micelle concentration, pyrene solubilization, micelle size distribution, and association number per micelle. Based on the amphiphilic balance, PEG-b-Pys formed core-shell type polymer micelle. The association number of PEG2k-b-Py was higher than that of PEG5k-b-Py, suggesting the degree of phase separation strongly depended on PEG Mn. Furthermore, the adsorption of PEG-b-Py copolymer onto silica nanoparticles as dispersant was studied to estimate the effect of PEG Mn in the copolymers and their solubility in the medium on the adsorption. Adsorbed density of PEG2k-b-Py copolymer onto silica nanoparticle was higher than that of PEG5k-b-Py, which was significantly correlated with the degree of phase separation. Furthermore, the adsorbed amount of copolymer increased with the increase in ionic strength due to the reduced solubility of PEG in the buffer solution. The resultant dispersion stability was highly correlated with the graft density of copolymer onto silica surface. However, the stability of PEG2k-b-Py coated particles was lower than that with PEG5k-b-Py, this is attributed to the relatively thin layer of PEG at the silica surface, which cannot provide the system with sufficient steric stabilization as the salt concentration increases. These fundamental investigations for the surface modification of the nanoparticle provide the insight into the highly stable colloidal dispersion, particularly in the physiological condition with high ionic strength.

Tuning the Electronic Properties and Acid-Response Behavior of N-Heteroacene-Based π-Conjugated Liquids by Changing the Number of π-Conjugated Substituents

We have designed and synthesized two room-temperature-fluorescent π-conjugated liquids based on the N-heteroacene framework (1 and 2). These two π-conjugated liquids, which contained one and two thiophene rings, respectively, exhibited different electronic properties and rheology behaviors. Single-crystal X-ray analysis of dithiophene-appended compound 4 revealed that two thiophene rings hindered the interactions of the imino N atoms with acids through the formation of interactions between the S atoms of the thiophene rings and the imino N atoms of the pyrazine group. On the other hand, monothiophene-appended molecules 1 and 3 each contained an unhindered imino N atom on the opposite site to the thiophene ring. Upon dissolving various acids with different pKa values in compounds 1 and 2, these slight structural differences gave rise to marked differences in their acid-response behaviors, thereby resulting in the emission of variously colored fluorescence in the liquid state. Furthermore, when acids with lower pKa values was dissolved in compounds 1 and 2, phase transition occurred from an isotropic liquid state to a self-organized liquid-crystalline phase.

Stimuli-Responsive Polymer Materials for Creation of Biointerfaces

In this review, we introduce the biorecognition-driven stimuli-responsive surface and hydrogels. The first attention focuses on recent advances in the development of functionalizable antifouling coatings and their applications in label-free optical biosensors. Approaches to the development of antifouling coatings, ranging from self-assembled monolayers and PEG derivatives to low-fouling polymer brushes and polymerized gels, are reviewed. Preparation of antifouling coatings and the functionalization of antifouling coatings with bioreceptors are introduced, and the application example of biofunctional coating with fouling properties is discussed. Special attention is given to biofunctional coatings for label-free bioanalysis of blood plasma and serum for medical diagnostics. The following focus is fed light on the biorecognition-based stimuli-responsive hydrogels. We will discuss on peptides and proteins recognition system of stimuli-responsive hybrid hydrogel composed of synthetic polymers and biopolymers.

PEGylation for biocompatible surface

Abstract Fouling corresponding to nonspecific protein adsorption is a key problem for many medical and biotechnological applications. The problem is most critical when complex biological media such as blood or blood plasma contact the surfaces of artificial materials. The proteins that adsorb on the biomaterial surface determine subsequent responses, including blood coagulation, platelet activation, complement activation and inflammation, and the final performance of the material. The development of technologies by which antifouling surfaces of biomedical materials can be prepared is a central challenge for contemporary research. Surface coatings based on poly(ethylene glycol) (PEG), a nontoxic and nonimmunogenic polymer, have been used for the modification of various biomedical surfaces (PEGylation). The high reactivity of PEG terminal makes the introduction of functional group easy to tether to the material’s surface. In this chapter, we highlight the construction of the PEG modified surface and its application to biological and biomedical fields. A PEG modified biocompatible surface is prepared by the various and effective surface coating method for substances and shows the characteristic features based on the properties of PEG.