It is my great pleasure to welcome all of you to the POLY-CHAR 2026 conference, Chiang Mai, Thailand, held under the theme “Smart, Sustainable & Data-Driven Polymeric Materials: From Molecular Design to Circular Applications.” This theme aims to help promote cross-disciplinary understanding between the classical branches of polymer science and some of the more avant-garde fields. The conference theme covers topics of special significance at present, such as sustainability, recyclability, energy, health, security, and AI. In addition to scientific programs, POLY-CHAR has always placed special emphasis on international collaboration, promotion of young scientists, and providing a collegial environment. It should also be noted that a good balance between gender and senior and young scientists has and will be sought throughout both the organization and duration of the conference. Beyond the academic program, Chiang Mai offers a truly unique cultural and natural experience. Known as the “Rose of the North,” the city is surrounded by scenic mountains and lush countryside, and is renowned for its centuries-old temples, vibrant night markets, and warm Thai hospitality. Notably, the conference coincides with the Loy Krathong Festival, one of Thailand’s most spectacular cultural celebrations. During this period, thousands of lanterns illuminate the night sky while candle-lit floats drift along the rivers, creating an unforgettable atmosphere that we hope you will enjoy. We sincerely hope that you will join us in Chiang Mai, Thailand, and contribute to the scientific exchange and success of POLY-CHAR 2026. We look forward to welcoming you in person.