Segmented organosiloxane copolymers. 1. Synthesis of siloxane—urea copolymers

Siloxane—urea linked segmented copolymers were synthesized from α,ω-bis(aminopropyl)poly dimethylsiloxane oligomers and various aromatic and cycloaliphatic diisocyanates such as MDI, TDI and H-MDI. Molecular weights of the siloxane oligomers were varied in the range of 1000–4000 g mole−1 and high molecular weight linear copolymers were obtained by employing homogeneous solution polymerization techniques. The solvent used during the reactions has a very critical role on the average molecular weight of the final product. Bis(2-ethoxy ethyl) ether (EEE) and THF were most useful. Chain extenders such as aliphatic or cycloaliphatic diamines were also used in some reactions and in this case polar cosolvents such as NMP were also required. The yields were usually very high and the amorphous products obtained from the simple stoichiometric linking reaction were soluble in various common organic solvents. Formation of urea linkages during the polymerization were followed by FTi.r. spectroscopy. The copolymers were characterized by g.p.c. and intrinsic viscosity measurements, FTi.r., n.m.r. and thermal analysis. All these results together with mechanical characterization described in the accompanying second paper of this series indicate the formation of novel, segmented elastomeric siloxane—urea copolymers.