1124189 IPN interpenetrating polymer network 392 3612552 semi-IPN semi-interpenetrating polymer network 142 2883883 IPNs interpenetrating polymer networks 117 3394233 semi-IPNs semi-interpenetrating polymer networks 53 3447228 SIPN semi-interpenetrating polymer network 34 1988984 SIPNs semi-interpenetrating polymer networks 22 3612549 Semi-IPN Semi-interpenetrating polymer network 3