Low friction thermoplastic polyurethane coatings imparted by surface segregation of amphiphilic block copolymers

This study aims to hydrophilize thermoplastic polyurethane (TPU) surface via selective segregation of amphiphilic block copolymers from bulk TPU matrix, namely “inverted grafting-to” approach. To this end, hydrophilic poly(ethylene glycol) (PEG) polymer chain was employed in either diblock (polycaprolactone-b-poly(ethylene glycol) (PCL-b-PEG)) or triblock (poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEG-b-PPO-b-PEG)) amphiphilic copolymer additives in polymer matrix. Greatly reduced water contact angles, as low as ca. 13°, from ≥90° for bare substrate proved the successful hydrophilization of TPU surface by this approach, although the degree of hydrophilization was significantly affected by the structure and concentration of embedded amphiphilic copolymers. Moreover, PEG-functionalized TPU surfaces in this approach displayed a reduction of coefficient of friction (COF) by two orders of magnitude. Given that TPU is a widely used material for urinary catheter or other medical devices, we demonstrated a first promising application as lubricious coating to TPU-based urinary catheter tubes.