Seyed Amin Mirmohammadi

Thermoresponsive magnetic composite gels based on poly( N‐ isopropylacrylamide) (PNIPAm) and its copolymers with N,N ‐dimethylaminopropylacrylamide (DMAPAA) were prepared by in situ formation of Fe ₃ O ₄ nanoparticles within the gel matrices. DMAPAA was introduced as a hydrophilic comonomer to improve the swelling stability of PNIPAm gels in concentrated iron ion solutions and to investigate its effect on nanoparticle formation, crystallite size, magnetic heating behavior, and adsorption properties. Pure PNIPAm gels exhibited severe deswelling in iron ion solutions due to the salting‐out effect, resulting in low magnetite content (5.9 wt%). In contrast, copolymerization with DMAPAA significantly improved gel swelling stability, increasing the Fe ₃ O ₄ content to 9.5 and 14.2 wt% for NIPAm/DMAPAA compositions of 900/100 and 800/200 mol/m ³ , respectively. XRD analysis confirmed the formation of magnetite nanoparticles (MNPs) with crystallite sizes of 9.4–11.1 nm. TEM observations revealed more uniformly dispersed MNPs with well‐defined morphologies in the copolymer gels compared with pure PNIPAm gels. Magnetic heating experiments under an alternating magnetic field demonstrated that the temperature rise increased with increasing magnetite content, while the thermoresponsive behavior of PNIPAm was preserved after nanoparticle formation. The copolymer gels exhibited broader and more gradual volume transitions because of the increased hydrophilicity introduced by DMAPAA. Bisphenol A (BPA) adsorption experiments demonstrated temperature‐dependent adsorption behavior associated with the hydrophilic–hydrophobic transition of PNIPAm. However, increasing DMAPAA content reduced BPA adsorption because of the enhanced hydrophilicity of the copolymer network. These results demonstrate that DMAPAA copolymerization is an effective strategy for controlling MNP incorporation and magnetic heating performance while maintaining thermoresponsive properties.

To address the limitations of poly (lactic acid) (PLA), it was blended with poly (methyl methacrylate) (PMMA) as a toughening component, using MgO nanoparticles (NPs, 0.075–0.15 wt%) as a catalyst. SEM pictures confirmed the good miscibility of the blends. Mechanical tests showed a slight decrease in elastic modulus and tensile strength for the PLA/PMMA125 sample containing 0.125% MgO. Yet, elongation at break rose by over 60% and impact strength increased by over 400% compared to pure PLA. Also, MgO facilitated the shifting of the glass transition temperature (T_g) of both polymers in DSC curves. Additionally, the absence of cold crystallization in PLA, coupled with reductions in its melting temperature (T_m) and crystallinity, were identified as critical factors contributing to improved miscibility within the reactive blend. Melt flow index (MFI) evaluation indicated a decrease in viscosity, while water contact angle measurements revealed an increase in polar groups on the surfaces of the MgO-containing samples. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirmed the effective distribution and dispersion of NPs throughout the blend, along with a significant decrease in crystallinity. Moreover, DFT calculations were performed to better understand the role of MgO in the reaction. The findings offered key insights into the reaction mechanism, confirming that MgO plays a crucial role in facilitating the transesterification between PLA and PMMA. These findings underscore the enhanced performance of exchange reactions between the active groups of both polymers in the presence of MgO, leading to the formation of PLA-PMMA copolymers with superior miscibility and mechanical properties. Finally, a cell culture assay confirmed the blend’s non-toxicity, showing its versatile potential.

Wood plastic composites (WPCs) consisting of high density polyethylene (HDPE) reinforced with high-loading (55 wt%) of wood flour (WF) were fabricated with melt-blending technique. In this compounding method, processing parameters such as different mixing temperatures (of 165, 180 and 195°C), mixing times (of 5, 10 and 15 minutes) and coupling agent contents (of 2 and 4 wt%) were evaluated. Prepared specimens were analyzed with tensile, Izod, shore D, DMTA, short-term creep, DSC, TGA, water absorption and water contact angle characterizations. Results revealed that mixing temperature of 180°C, mixing time of 10 minutes and coupling agent concentration of 4 wt% were found as the best processing conditions. The mentioned conditions provided enhanced dispersion of WF particles within the HDPE matrix, due to optimum viscosity of the polymer melt and effective residence time of compound in the mixer, and beside them efficient interfacial adhesion between WF and polymer matrix.