Preparation and property investigation of chain end functionalized cis-1,4 polybutadienes via de-polymerization and cross metathesis of cis-1,4 polybutadienes

Abstract

The transformation of cis-1,4-polybutadiene (PBD) to chain end functionalized propyltriethoxysilane (PBD-Si(OEt)₃), trimethylsilane (PBD-SiMe₃), phosphate (PBD-Phosphate), di-tert-butylphenol (PBD-Phenol) and propane epoxide (PBD-PO) cis-1,4-polybutadienes via depolymerization by the Grubbs (II) catalyst and tandem cross metathesis employment of the corresponding chain transfer reagents (CTAs) has been developed. The formation of difunctionalized cis-1,4 polybutadiene (DF) with controlled molecular weight takes place, along with minor amounts of a mono-functionalized polymer (MF) and a non-functionalized polymer (NF) as evidenced by NMR, IR, GPC and MALDI-TOF. The precise cis-1,4 regiocontrol of functionalized rubber leads to further investigation of thermal-mechanical properties of elastomers. The PBD-Phosphate and PBD-Phenol exhibit enhanced thermal properties when the decomposition onset temperature was increased and the decomposition rate was also decreased compared to those of pure cis-1,4 polybutadiene. PBD-Si(OEt)₃ was hydrolyzed on SiO₂ and the resultant product was utilized as a compatibilizer for improving the interfacial interaction between filler SiO₂ and matrix cis-1,4 polybutadiene. As a result, improvements of the resultant vulcanizate properties regarding elongation at break, tensile strength and loss factor are observed. The established knowledge of the correlation of functional groups in the chain end with thermal-physical properties could provide guidelines to develop high performance rubber materials from various conjugated diene elastomers.