Creating porous tubes by centrifugal forces for soft tissue application

Chemically crosslinked poly(2-hydroxyethyl methacrylate) (PHEMA) tubes were synthesized by applying centrifugal forces to propagating polymer chains i n solution. Initiated monomer solutions, with a composition typical for PHE MA sponges, were placed into a cylindrical mold that was rotated about its long axis. As polymerization proceeded, phase separated PHEMA formed a sedi ment at the periphery under centrifugal action. The solvent remained in the center of the mold while the PHEMA phase gelled, resulting in a tube. By c ontrolling the rotational speed and the formulation chemistry (i.e., monome r, initiator and crosslinking agent concentrations), the tube dimensions an d wall morphology were manipulated. Tube manufacture was limited by a criti cal casting concentration [M](c), above which only rods formed. All tubes h ad an outer diameter of 2.4 mm, reflecting the internal diameter of the mol d and a wall thickness of approximately 40-400 mum. Wall morphologies varie d from interconnecting polymer and water phases to a closed cell, gel-like, structure. Concentric tubes were successfully prepared by using formulatio ns that enhanced phase separation over gelation/network formation. This was achieved by using formulations with lower concentrations of monomer and cr osslinking agent and higher concentrations of initiator. This technique off ers a new approach to the synthesis of polymeric tubes for use in soft tiss ue applications, such as nerve guidance channels. (C) 2001 Elsevier Science Ltd. All rights reserved.