Biodegradable implants based on photo-cross-linked aliphatic polycarbonates for long-acting contraception

In this study,a new class of biodegradable contraceptive implants was prepared via the UV irradiation molding method,among which,progestin levonorgestrel(LNG)was used as a model drug.Photo-cross-linked aliphatic polycarbonates(APCs),namely,poly(trimethylene carbonate-co-2,2′-dimethyltrimethylene carbonate)[P(TMC-co-DTC)]elastomers,were used as the drug delivery matrix.The results obtained from the degradation experiments carried out in Sprague-Dawley(SD)rats showed that the cross-linked elastomer had the degradation characteristics of the surface erosion degradation mechanism,with no generation of acid degradation products,and excellent form-stability,which met the performance requirements of the matrix for a long-acting sustained-release delivery system.The in vitro cytotoxicity tests and histological and immunohistochemical evaluations showed good biocompatibility and biosafety of the elastomer matrix material and contraceptive implants.Subsequently,the implant formulations were screened by in vitro release experiments,and their release kinetics were explored.Finally,in the evaluation study of the in vivo anti-fertility effect,the implants exhibited excellent dimensional stability and were degraded by a surface erosion mechanism.LNG achieved a stable and sustained release in female SD rats,maintaining a long-acting contraceptive duration of up to 4 months.The contraceptive implants obtained in this study could be used to address the limitations of currently available formulations,which required secondary surgical removal and a single means of regulating drug release kinetics.Therefore,these implants could provide a new option for birth control needs and may be of significance in reducing the incidence of induced abortion and protecting female fertility.

Magnesium Acetate Used as an Effective Catalyst for Synthesizing Aliphatic Polycarbonates via Melt Transesterification Process

High-molecular-weight aliphatic polycarbonates（APCs） were synthesized through a two-step transesterification process under solvent-free conditions. Oligomers with equal numbers of hydroxyl and phenyl carbonate terminal groups could be easily controlled by using equimolar amounts of diphenyl carbonate（DPC） and aliphatic diols as feedstocks in the first step. In the second step, the high-molecular-weight APCs can be obtained by connecting -OH with -OC（O）OC6H5 end-group upon removing the generated phenol at reduced pressure. Mg（OAc）2 was found to be the best catalyst for this process among the screened catalysts, which gave the poly（l,4-butylene carbonate）（PBC） a weight-average molecular weight（Mw） of 148600 and a yield of 84.8% under its suitable reaction conditions. In addition, based on the results of X-ray diffraction（XRD）, scanning electron microscopy（SEM） and fourier transform infrared spectroscopy（FTIR）, a possible reaction mechanism over Mg（OAe）2 was proposed for APCs synthesis.

Synthesis and properties of novel aliphatic polycarbonate from carbon dioxide with 1,2-butylene oxide and ε-caprolactone

A new degradable aliphatic poly(butylene-co-e-caprolactone carbonate) (PBCL) was synthesized through the terpolymerization of carbon dioxide, 1,2-butylene oxide (BO) and e-caprolactone (CL), a polymer supported bimetallic complex (PBM) was used as a catalyst. The terpolymers prepared were characterized by FT-IR,1H NMR, 13C NMR, WXRD and DSC. The hydrolysis tests were carried out to appraise the degradability of the copolymers.

STUDIES ON MISCIBILITY OF POLY (ε-CAPROLACTONE) AND ALIPHATIC POLYCARBONATE BLENDS AND DETERMINATION OF THEIR INTERACTION PARAMETER

In this paper the miscibility of poly (ε-caprolactone) (PCL) and aliphatic polycarbonate (APC) is studied by using DSC. The results show that PCL and APC are miscible in all ranges of composition. The interaction parameter between the polymers is calculated from the melting point depression data. Using optical microscope, the shapes of the PCL spherulites in the blends are observed.

Synthesis of CO2 Copolymer Based Polyurethane Foams

CO2-copolymer based polyurethane foams were synthesized and characterized in this paper. The foams were found to have higher strength and lower heat of combustion than the conventional polyether polyurethane foams. They may find wide applications in many fields.

EFFECT OF CHEMICAL STRUCTURE OF POLYCARBONATES ON ENTANGLEMENT SPACING

The master curves of a series of aliphatic polycarbonates （APCs） with different lengths of methylene segments in the repeat unit were obtained by dynamic rheological measurements. The plateau modulus and entanglement molecular weight were determined and cross-checked by different methods. Though having distinct difference in chemical structure of repeat units, both APCs and bisphenol-A polycarbonates have the similar entanglement weight and entanglement spacing. On the other side, the plateau modulus decreases with increasing the length of the side group of aliphatic polycarbonates with different side-chain lengths in the literature. The packing length model can explain the relationship between chain structure and entanglements.