2-oxepane-1,5-dione: a precursor of a novel class of versatile semicrystalline biodegradable (co)-polyesters

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Synthesis of 2-oxepane-dione (OPD)

OPD and

εεεε

CL Copolymerization

$ 12 3 455& 3 # 6 % 7 #$8 % 9 Sn(IV) alkoxides are very efficient initiators.

Al(OiPr)3, Y(OiPr)3are not suitable because of detrimental

complexation of the initiator to the C=O group of the OPD units

0 2 4 6 8 10 12 0 5 10 15 20 Time (weeks) W ei gh t lo ss ( % ) A B

Hydrolytic degradation

Conditions : pH=7.4 at 37 C ; P(OPD-co-εCL) ( Mn=35000 ; 30 mol% of OPD)

40 60 80 100 120 140 160 0 0.2 0.4 0.6 0.8 1

OPD molar ratio

Tm

(

OC

)

Thermal properties :

P(OPD-co-

εεεε

CL), a semicrystalline copolymer

200 220 240 260 280 300 320 0 0.2 0.4 0.6 0.8 1

OPD molar ratio

Tg (K ) Experimental Tg Fox Equation Cell parameters ( ) A B C δ PCL 7.49 4.98 17.05 6.2 2.98 P(OPD) 6.80 5.18 17.17 6.2 2.82 Regular and continuous increasing Tm PCL and P(OPD) units are isomorphous

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Thermal degradation

: sample : P(OPD-co-εCL) ; FOPD=0.3

-5 -4 -3 -2 -1 0 2.2 2.3 2.4 2.5 2.6 1/T (x 103₎ ln k

Mechanical properties

Copolymer P(OPD-co-OPD), FOPD=0.33 CAPA 650 P(OPD-co-OPD), FOPD=0.34 P(OPD-co-OPD), FOPD=0.33 P(OPD-co-OPD), FOPD=0.33 Mn (K) 42 50 εb (%) 800 1000 σb (MPa) 26 36 σy (MPa) 15 13

Acknowledgments : The authors are grateful to SOLVAY S. A. (Belgium) for support and discussions. They thank SSTC (PAI 503). Philippe Lecomte is chercheur Qualifi by the FNRS.

P(OPD-co-εCL) containing 30 mol% OPD exhibits a Tm= 90 C, which opens up new opportunities for applications that

require a higher service temperature than PCL, i. e., packaging applications

P(OPD-co-εCL) containing 30 mol% of OPD is stable up to 140 C under nitrogen for one hour, such that processing by extrusion is possible.

Degradation of P(OPD-co-εCL) is faster than PCL (Ea=92kJ/mol) because of the

ketone group of the OPD units

Above a critical molecular weight, the tensile and impact properties are comparable to those ones of commercially available PCL (CAPA, Solvay)

Impact energy (kJ/m2₎

18-20 No breaking No breaking

The C=O group imparts higher hydrophilicity, which has a key role in the increase of the hydrolytic degradation rate compared to PCL After 20 weeks SEM image after immersion

After 9 days

Crosslinking under UV

Exposure of P(OPD-co-εCL) (FOPD=0.3) to UV induces loss of solubility. Frequency sweep

experiments show higher elasticity above Tm. An increased brittelness was shown by tensile properties. No significant effect on Tm

and∆Hmwas observed. The C=O group of the OPD units is at the origin of this behavior.

33K 42K 50K After 0 days k (%/min) determined by Isothermal TGA Ea=75kJ/mol (under N2) FOPD=0.3 0 5 10 15 20 25 0 5 10 15 20 Time (weeks) W at er a bs or p tio n (% ) A B ε