Summary: It has been a real challenge to form carbon nanotube (CNT)/polymer composites where CNTs are well‐dispersed in the polymer matrix and the interactions between CNTs and polymers are effectively strong. In this paper, we applied surface‐initiated, ring‐opening polymerization (SI‐ROP) of p‐dioxanone (PDX) to shortened single‐walled carbon nanotubes (s‐SWCNTs) and successfully formed s‐SWCNT/PPDX composites (see Figure). Due to intimate interactions between s‐SWCNTs and PPDX, we observed dramatic changes in PPDX properties upon the formation of the composites: 10%‐weight‐loss‐temperature of PPDX increased by 20 °C (measured by thermogravimetric analysis) and the patterns of Tg and Tm were greatly altered. We did not observe any noticeable peaks from the composite up to 120 °C in differential scanning calorimetry (DSC), while DSC data of PPDX itself showed Tg and Tm at ?13.4 and 103 °C respectively.