Synthesis of highly crystalline poly(dimethylbutadiene) (PDMB) by radiation-induced inclusion polymerization: A comparison with PDMBs synthesized by bulk and emulsion polymerization

Poly-2,3-dimethylbutadiene (DMBD) has been synthesized by the radiation-induced inclusion polymerization technique. 2,3-DMBD was included as a clathrate in the channels of thiourea crystals and polymerized with 300 kGy into a crystalline high trans-1,4-polydimethylbutadiene (PDMB) in high yield. For comparison 2,3-DMBD was also polymerized by bulk radiolysis in high vacuum at 150, 300 and 600 kGy. The resulting PDMB was obtained in very low yields and had a microstructure completely different from that observed on PDMB synthesized by inclusion polymerization and more similar to the structure of an emulsion-PDMB prepared by a free radical initiator. Trans-PDMB prepared by inclusion polymerization was characterized by a crystalline melting point at 272 °C.The radiation chemical yield for the PDMB obtained by inclusion polymerization was found G=212 monomer units (in PDMB)/100 eV. This value is 23.5 times higher that measured in PDMB prepared by bulk radiolysis of the monomer.