Peerasak Paoprasert

Preparation of biocompatible and antibacterial carbon quantum dots derived from resorcinol and formaldehyde spheres

Green or yellow emitting carbon quantum dots (CQDs) were prepared through the combination of bottom-up and top-down approaches from resorcinol and formaldehyde. The prepared CQDs showed characteristic fluorescence behavior depending on the compositional or structural features. Both CQD-S (green emitting) and CQD-P (yellow-emitting) were physiologically stable and biocompatible as cancer cell bioimaging agents. Especially, silver nanoparticle (Ag NP)-decorated CQDs revealed very good antibacterial activity for Gram-positive S. aureus and Gram-negative E. coli.

Preparation and temperature-responsive behavior of crosslinked polymers between poly(N-isopropylacrylamide) and natural rubber

Stimuli-responsive polymers are considered as smart materials as they can respond to subtle changes in external stimuli, such as pH, temperature, light, magnetic field, etc. Natural rubber (NR) is one of the most important renewable resources, offering excellent flexibility and fatigue resistance. In this work, temperature responsiveness was introduced to NR via a crosslinking reaction with poly(N-isopropylacrylamide) (PNIPAM) using benzoyl peroxide as a free radical crosslinker. PNIPAM was chosen because it is a well-known temperature-responsive polymer with a lower critical solution temperature near the human body temperature, enabling applications in biomedical fields. The crosslinked materials between PNIPAM and NR were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The effects of polymer and crosslinker concentration, reaction temperature, and reaction time on the gel content were studied. The temperature responsiveness of the crosslinked polymers was investigated and the lower critical solution temperature was found to be in the range 30-34 °C. Based on these results, we demonstrated a straightforward strategy for preparing crosslinked polymers between PNIPAM and NR. The introduction of temperature responsiveness into NR will lead to new responsive rubber-based materials and expand the range of potential applications.

Temperature-responsive crosslinked materials prepared from natural rubber and poly( N -vinylcaprolactam)

A straightforward method for functionalizing natural rubber (NR) with poly(N-vinylcaprolactam) (PNVCL), a temperature-responsive polymer having lower critical solution temperature (LCST) near human body temperature, has been successfully developed using free radical crosslinking reaction. Effects of polymer and initiator concentrations, reaction temperature, and reaction time on immobilization percentage of the synthesized polymer were investigated. Results showed 100% immobilization percentage when using 100 phr of PNVCL, 10 phr of benzoyl peroxide at 75 °C within 36 h. For the temperature responsiveness, the water swelling, water contact angle, and dye release of the crosslinked NR were measured. Its LCST ca. 32-34 ˚C was close to that of the pristine PNVCL. The dye adsorption studies revealed the Langmuir isotherm indicating monolayer coverage. Dye release could be triggered by increasing the temperature above the LCST, suggesting its potential uses in drug release technology. In addition, this temperature-responsive NR would potentially be used as a novel responsive rubber-based material in various applications, such as sensors and biomedical materials.