Influence of PLLA nanoparticle addition on the properties of semiinterpenetrating polymer networks

Novel nanocomposite semi-interpenetrating (semiIPN) polymer networks of poly(N-isopropylacrylamide) (PNIPAAm) and alginate (Alg-PNIPAAm), containing poly-L-lactide (PLLA) nanoparticles were prepared and morphological, thermal, chemical, thermomechanical and rheological properties were investigated. The successful incorporation of PLLA nanoparticles into the semiIPN gels was confirmed by field emission scanning electron microscope (FESEM) and infrared spectroscopy (FT-IR). FESEM microscopy also showed the different pore size and pore size distribution of the nanocomposite respect to the primary gel. The resulting morphology was related to the thermal and viscoelastic properties exhibited by the materials. The introduction of PLLA nanoparticles does not affect the thermal stability of the gel and does not modify the lower critical solution temperature (LCST), while interferes with the contraction behavior of the gel, leading to a different thermal expansion coefficient observed for the nanocomposite. Furthermore, rheological results suggest a different degree of crosslinking for the nanocomposite gel, due to the presence of PLLA nanoparticles that probably hinders the reaction of crosslinking of PNIPAAm. The prepared NPs-AlgPNIPAAm-semiIPN gels with thermosensitive and biodegradable properties are very interesting from both applied and fundamental perspectives and make this system a good candidate for practical application in drug delivery and controlled drug release.