Stimuli-responsive 4-acryloylmorpholine/4-acryloylpiperidine copolymers via nitroxide mediated polymerization

Improving Recycled Poly(lactic Acid) Biopolymer Properties by Chain Extension Using Block Copolymers Synthesized by Nitroxide-Mediated Polymerization (NMP)

The aim of this contribution is to assess the use poly(styrene-co-glycidyl methacrylate-b-styrene) copolymers synthesized by nitroxide mediated polymerization (NMP) as chain extenders in the recycling of poly(lactic acid) biopolyester. Concisely, the addition of such block copolymers during the melt processing of recycled poly(lactic acid) (rPLA) leads to important increases in the viscosity average molecular weight of modified polymeric materials. Molar masses increase from 31,000 g/mol for rPLA to 48,000 g mol^-1 for the resulting rPLA/copolymer blends (bPLA). Fortuitously, this last value is nearly the same as the one for pristine PLA, which constitutes a first piece of evidence of the molar mass increase of the recycled biopolymer. Thermograms of chain extended rPLA show significant decreases in cold crystallization temperature and higher crystallinity degrees due to the chain extension process using NMP-synthesized copolymers. It was found that increasing epoxide content in the NMP-synthesized copolymers leads to increased degrees of crystallinity and lower cold crystallization temperatures. The rheological appraisal has shown that the addition of NMP synthesized copolymers markedly increases complex viscosity and elastic modulus of rPLA. Our results indicate that P(S-co-GMA)-b-S) copolymers act as efficient chain extenders of rPLA, likely due to the reaction between the epoxy groups present in P(S-co-GMA)-b-PS and the carboxyl acid groups present in rPLA. This reaction positively affects viscometric molar mass of PLA and its performance.

A novel multi-stimuli-responsive theranostic nanomedicine based on Fe3O4@Au nanoparticles against cancer

A novel multi-stimuli-responsive theranostic nanomedicine was designed and fabricated by the conjugation of a thiol end-capped poly(N-isopropylacrylamide-block-acrylic acid) (HS-PNIPAAm-b-PAA) onto Fe₃O₄@Au nanoparticles (NPs) followed by physical loading of doxorubicin hydrochloride (Dox) as a general anticancer drug. For this purpose, Fe₃O₄@Au NPs were fabricated through small Au nanolayer grown on larger magnetic NPs. A HS-PNIPAAm-b-PAA was synthesized through an atom transfer radical polymerization (ATRP) approach, and then conjugated with as-synthesized Fe₃O₄@Au NPs by Au-S bonding. The Dox loading capacity of the synthesized Fe₃O₄@Au/Polymer theranostic NPs was calculated to be 81%. The theranostic nanomedicine exhibited excellent in vitro drug release behavior under pH and thermal stimuli. The anticancer activity evaluation using MTT assay (against MCF7 cells) revealed that the fabricated Fe₃O₄@Au/Polymer has high potential as theranostic nanomedicine for cancer therapy of solid tumors. This nanosystem can also applied in photothermal therapy, hyperthermia therapy, and their combination with chemotherapy due to presence of gold and Fe₃O₄ nanomaterials in its structure.