Poly(cyclohexene carbonate)(PCHC) is one of the few biodegradable polymers maintaining dimension stability over 100℃ due to its high Tg of 115℃

but PCHC is quite difficult for melt processing because of its brittleness.In this work

backbone modification route was proposed by intercalating soft ethylene carbonate segments among the hard cyclohexene carbonate segments

where the terpolymerization of carbon dioxide (CO2)

ethylene oxide(EO) and cyclohexene oxide (CHO) was carried out under ternary rare earth metal coordination catalyst prepared from Y(CCl3COO)3

glycerin

and ZnEt2.The terpolymerization was carried out at 70℃ in a 2000 mL autoclave for 10 h.The obtained terpolymers were subjected to 1H-NMR

13C-NMR- experiments for structure analysis

Gel permeation chromatograhy (GPC) was used to determine the number average molecular weight and its polydispersity

and dynamic mechanical analysis (DMA) was used for thermomechanical studies

the mechanical performance was done with a ZWick/Z010 multifunction mechanical testing instrument.The catalytic activity was between 425 g/(mol Zn h) and 691 g/(mol Zn h)

depending on the molar ratio of CHO to EO

and the number average molecular weight ranged between 7.2×104 and 7.9×104

with polydispersity index changing from 3.17 to 3.57 .The optimal catalytic activity reached 691 g/(mol Zn h) when equal molar ratio of EO and CHO was added

and the obtained terpolymer showed a number average molecular weight of 7.9×104 with polydispersity index of below 3.5. The absorption peaks in 1H-NMR spectra of poly(ethylene carbonate)

poly(cyclohexene carbonate) and related terpolymer were assigned.For the terpolymer obtained from equal molar ratio of EO to CHO

heteronuclear multiple-bond correlation (HMBC) experiments showed that alternating linkages between ethylene carbonate and cyclohexene carbonate were only 269% in the terpolymer

and random structure consisting of ethylene carbonate (EC) units and cyclohexene carbonate (CHC) units was predominant.For the terpolymer obtained from equal molar ratio of EO to CHO

the dynamic mechanical analysis (DMA) spectra showed three peaks

one peak at -80℃ was attributed to a second transition in the terpolymer

the another two peaks appeared at 20℃ and 80～100℃ were assigned to the glass transitions of the polymer related to ethylene carbonate segments and cyclohexene carbonate segments

respectively

the existence of two glass transitions at different temperatures indicated that the existence of soft and hard segments in the backbone.Introducing EO as the third comonomer was effective to solve the brittleness of PCHC making it melt processable

moreover

the thermal and mechanical properties of the terpolymer can be adjusted by changing the molar ratio of EO and CHO in comonomers.For the terpolymer obtained from equal molar ratio of EO to CHO

the Young’s modulus at 25℃ was 9957 MPa

and its tensile strength was 271 MPa with elongation at break of 42.3%.When the temperature was raised to 50℃

the Young’s modulus maintained 8687 MPa

and its tensile strength was 15.2 MPa with elongation at break of 576%.As a reference

poly(propylene carbonate) lost mechanical strength at 50℃

the Young’s modulus at 40℃ was found to be 568 MPa

and its tensile strength was 2.1 MPa with elongation at break of 1814.9%.Therefore

by means of terpolymerization of CO2

EO and CHO

a melt processable biodegradable polymer with improved dimension stability at higher temperatures was prepared.