Abstract
Poly(D,L-lactide) synthesis using tin(II) 2-ethylhexanoate initiated ring-opening polymerization (ROP) takes over 30 hours in bulk at 120 °C. The use of microwave makes the same bulk polymerization process with the same initiator much faster and energy saving, with a reaction time of about 30 minutes at 100 °C. Here, the poly(lactide) synthesis was done in a microwave reactor, using frequency of 2.45 GHz and maximal power of 150 W. The reaction temperature was controlled via infra-red system for in-bulk-measuring, and was maintained at 100 °C. Different molar ratios of monomer and initiator, [M]/[I], of 1,000, 5,000 and 10,000 were used. The achieved average molar masses for the obtained polymers (determined by gel permeation chromatography) were in the interval from 26,700 to 112,500 g/mol. The polydispersion index was from 2.436 to 3.425. For applicative purposes, the obtained material was purified during the procedure of microsphere preparation. Microspheres were obtained by spraying a fine fog of polymer (D,L-lactide) solution in tetrahydrofuran into the water solution of poly(vinyl alcohol) with intensive stirring.
Highlights
Polymers based on lactic acid deserve great attention because they decompose by hydrolysis in the human body into nontoxic metabolites
The poly(lactide) synthesis is carried out by ring-opening polymerization according to the scheme given in the Figure 1
Such microspheres can be used as polymer matrices for the production of devices for controlled release of medicinal substances, since the diameter of the microspheres is appropriate for phagocytosis by macrophages
Summary
Polymers based on lactic acid deserve great attention because they decompose by hydrolysis in the human body into nontoxic metabolites. The traditional method of poly(lactide) (PLA) synthesis required rigorous conditions: a high vacuum, long polymerization times and the consumption of great quantities of energy, using metal or metal oxide as a catalyst to speed up the reaction and minimize the pyrolysis by reducing the temperature [21–29]. Microwave radiation has numerous advantages compared to conventional heating: homogeneous heating of the whole volume of the reaction mixture, high transfer energy per unit of time, improved yield, the possibility of the process acceleration and synthesis without using great quantity of the solvent. In an industry where time is money, the dramatic rate acceleration and increased purity and yields of microwave assisted reactions make them attractive for high-produced polymers. D,L-lactide by microwave irradiation under atmosphere was investigated Both lactic acid and its oligomer are polar molecules, so they can absorb microwave energy to increase the temperature
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
