Rubber elasticity of poly(n‐butyl acrylate) networks formed with multifunctional crosslinkers

The rubber elasticity characteristics of poly( n ‐butyl acrylate) networks crosslinked with tetrafunctional (EGDM and TEGDM), hexafunctional (TMPTM), and octafunctional (PETMA) vinyl crosslinkers were investigated. Both gel—sol analyses and crosslinking efficiency theories were used to evaluate the chemical crosslink contribution v c and the entanglement contribution v p to the elastically effective network chains v e , and the effect of the crosslink junction functionality f on the front factor g . The front factors obtained were in the range of 0.50–0.92, depending upon the network system and the counting method for v c . The relationship of g = [( f − 2)/ f ]/〈 r 2 〉/〈 r 2 〉 o seems reasonable in the case of the tetrafunctional and hexafunctional networks, but deviates in the case of the octafunctional network. It is also evident that the functionality scheme for the front factor could only be valid under the postulate of a high v p , which increases with increasing v c , especially in the high v c region near the Gaussian limit. The average energetic contribution to the retractive force of the present systems, expressed as F e /F , is −0.30 ± 0.1.