A novel biobased plasticizer made of cardanol is designed for poly(lactide) (PLA). This cardanol‐derived plasticizer, i.e., methoxylated hydroxyethyl cardanol (MeCard), is synthesized through methoxylation of the double bonds on the side chain of cardanol, and characterized by 1H NMR and mass spectrometry. The plasticization effect of MeCard on the molecular structure, morphology, thermal and mechanical properties of PLA is evaluated and compared to that of a commercial cardanol, i.e., hydroxyethyl cardanol (pCard). The plasticization efficiency of MeCard is demonstrated by a substantial decrease of the glass transition temperature and storage modulus together with a significant increase of the elongation at break as compared to neat PLA. Moreover, MeCard exhibits higher plasticization performance than pCard toward PLA. Such behavior is related to a higher miscibility and compatibility between PLA and MeCard thanks to the methoxylation of the double bonds on the side chain of cardanol as shown by SEM micrographs.
Morphological changes of solution-grown crystals (SGCs) of poly(l-lactide) (PLLA) following thermal treatment and enzymatic degradation were investigated using atomic force microscopy in terms of defects in the crystals. PLLA SGCs were grown from a dilute solution of acetonitrile at 5 °C. The obtained solution-grown monolamellar crystals have a lozenge-shaped morphology containing unique dimensions, with one side measuring 12 μm. To investigate enzymatic degradation behavior, PLLA SGCs were incubated in buffered solution with proteinase-K at 37 °C. The initial stage of enzymatic degradation of PLLA SGCs with proteinase-K occurs in loosely folding chains at the surface of the crystal. Thermally treated PLLA SGCs below the melting temperature showed an increase of the lamellar thickness of the SGCs at the treated temperature and partial surface erosion following enzyme exposure. These results indicate that less ordered chains exist throughout the lamellae and their thermal-induced chain extension makes them more susceptible to enzyme attack. 相似文献
Thermosensitive liquid suppositories (LSs) carrying the model antihypertensive drug metoprolol tartrate (MT) were developed and evaluated. The fundamental purpose of this work was to produce, for the first time, liquid MT suppositories based on biodegradable nanoparticles and optimize their rheological and mechanical properties for prospective rectal administration. The nanoparticle system was based on a biodegradable copolymer synthesized by ring opening polymerization (ROP) of glycolide (GL) and L,L-lactide (LLA). Biodegradable nanoparticles loaded with the model drug were produced by the o/o method at the first stage of the investigation. Depending on the concentration of the drug in the sample, from 66 to 91% of MT was released over 12 h, according to first-order kinetics. Then, thermosensitive LSs with MT-loaded biodegradable nanoparticles were obtained by a cold method and their mechanical and rheological properties were evaluated. To adjust the thermogelling and mucoadhesive properties for rectal administration, the amounts of major formulation components such as poloxamers (P407, P188), Tween 80, hydroxypropylcellulose (HPC), polyvinylpyrrolidone (PVP), and sodium alginate were optimized. The in vitro release results revealed that more than 80% of the MT was released after 12 h, following also first-order kinetics. It was discovered that the diffusion process was dominant. The drug release profile was mainly governed by the rheological and mechanical properties of the developed formulation. Such a novel, thermosensitive formulation might be an effective alternative to hypertension treatment, particularly for unconscious patients, patients with mental illnesses, geriatric patients, and children. 相似文献