Shape memory polymer foam: active deformation, simulation and validation of space environment

Shape memory polymer foam (SMPF) is being studied extensively as potential aerospace materials as they have high compression ratio, high specific strength and high specific modulus compared to other shape memory polymers. In this paper, a composite foam with shape memory epoxy (SMEP) as matrix and polyurethane (PU) as functional phase was prepared. The SMPF has been characterized by different analytical and testing methods, and its chemical crosslinking reaction and material properties have been studied. The SMPF was installed in the shape memory polymer composite (SMPC) flexible solar array system (SMPC-FSAS), and ground environment tests and orbital validation were performed. Considering the particularity of space environment, the thermal performance test of ground space environment can effectively test the reliability of shape memory performance. Finally, the SMPC-FSAS carried on SJ-20 satellite successfully deployed on geosynchronous orbit for the first time in the world. Moving forward, SMPF assesses the feasibility of applications in the space field and provides more valuable information.

Preparation and Properties of Autocatalytic Biobased Waterborne Polyol from Rosin Based Epoxy Resin

Due to the complex heterogeneous film forming process of two-component waterborne polyurethane (2K-WPU), the crosslinking reaction rate of 2K-WPU cannot meet the demand of efficient application in coatings. In order to improve the crosslinking reaction rate of 2K-WPU, a waterborne polyol containing tertiary amine groups was synthesized from rosin based epoxy resin and secondary amine compound, and then autocatalytic 2K-WPU was prepared by crosslinking the rosin based waterborne amino polyol with polyisocyanate. The structure of the polyol from rosin based epoxy resin was characterized with Fourier infrared (FT-IR) and nuclear magnetic resonance (NMR). The crosslinking kinetics and the crosslinked product of the rosin based waterborne amino polyol were also compared with a commercial acrylic polyol. It was shown from the results that the crosslinking reaction rate of the rosin based waterborne amino polyol was faster than that of the commercial acrylic polyol, which indicated the tertiary amine groups chemically bonded in the rosin based polyols could autocatalyze the crosslinking reaction of 2K-WPUs with catalysts free. The film of the rosin based waterborne amino polyol had excellent impact strength, adhesion, flexibility, hardness, gloss, fullness and solvent resistance, showing a good application prospect in the field of waterborne coatings.

Mechanically Robust and Flame-Retardant Polylactide Composites Based on In Situ Formation of Crosslinked Network Structure by DCP and TAIC

The addition of intumescent flame retardant to PLA can greatly improve the flame retardancy of the material and inhibit the dripping, but the major drawback is the adverse impact of the mechanical properties of the material. In this study, we found that the flame retardant and mechanical properties of the materials can be improved simultaneously by constructing a cross-linked structure. Firstly, a cross-linking flame-retardant PLA structure was designed by adding 0.9 wt% DCP and 0.3 wt% TAIC. After that, different characterization methods including torque, melt flow rate, molecular weight and gel content were used to clarify the formation of crosslinking structures. Results showed that the torque of 0.9DCP/0.3TAIC/FRPLA increased by 307% and the melt flow rate decreased by 77.8%. The gel content of 0.9DCP/0.3TAIC/FRPLA was 30.8%, indicating the formation of cross-linked structures. Then, the mechanical properties and flame retardant performance were studied. Results showed that, compared with FRPLA, the tensile strength, elongation at break and impact strength of 0.9DCP/0.3TAIC/FRPLA increased by 34.8%, 82.6% and 42.9%, respectively. The flame retardancy test results showed that 0.9DCP/0.3TAIC/FRPLA had a very high LOI (the limiting oxygen index) value of 39.2% and passed the UL94 V-0 level without dripping. Finally, the crosslinking reaction mechanism, flame retardant mechanism and the reasons for the improvement of mechanical properties were studied and described.

Nanoarchitectonics for High Adsorption Capacity Carboxymethyl Cellulose Nanofibrils-Based Adsorbents for Efficient Cu2+ Removal

In the present study, carboxymethyl cellulose nanofibrils (CMCNFs) with different carboxyl content (0.99–2.01 mmol/g) were prepared via controlling the ratio of monochloroacetic acid (MCA) and sodium hydroxide to Eucalyptus bleached pulp (EBP). CMCFs-PEI aerogels were obtained using the crosslinking reaction of polyethyleneimine (PEI) and CMCNFs with the aid of glutaraldehyde (GA). The effects of pH, contact time, temperature, and initial Cu2+ concentration on the Cu2+ removal performance of CMCNFs-PEI aerogels was highlighted. Experimental data showed that the maximum adsorption capacity of CMCNF30-PEI for Cu2+ was 380.03 ± 23 mg/g, and the adsorption results were consistent with Langmuir isotherm (R2 > 0.99). The theoretical maximum adsorption capacity was 616.48 mg/g. After being treated with 0.05 M EDTA solution, the aerogel retained an 85% removal performance after three adsorption–desorption cycles. X-ray photoelectron spectroscopy (XPS) results demonstrated that complexation was the main Cu2+ adsorption mechanism. The excellent Cu2+ adsorption capacity of CMCNFs-PEI aerogels provided another avenue for the utilization of cellulose nanofibrils in the wastewater treatment field.

Near-Infrared Light-Responsive Shell-Crosslinked Micelles of Poly(d,l-lactide)-b-poly((furfuryl methacrylate)-co-(N-acryloylmorpholine)) Prepared by Diels–Alder Reaction for the Triggered Release of Doxorubicin

In the present study, we developed near-infrared (NIR)-responsive shell-crosslinked (SCL) micelles using the Diels–Alder (DA) click reaction between an amphiphilic copolymer poly(d,l-lactide)20-b-poly((furfuryl methacrylate)10-co-(N-acryloylmorpholine)78) (PLA20-b-P(FMA10-co-NAM78)) and a diselenide-containing crosslinker, bis(maleimidoethyl) 3,3′-diselanediyldipropionoate (BMEDSeDP). The PLA20-b-P(FMA10-co-NAM78) copolymer was synthesized by RAFT polymerization of FMA and NAM using a PLA20-macro-chain transfer agent (PLA20-CTA). The DA reaction between BMEDSeDP and the furfuryl moieties in the copolymeric micelles in water resulted in the formation of SCL micelles. The SCL micelles were analyzed by 1H-NMR, FE-SEM, and DLS. An anticancer drug, doxorubicin (DOX), and an NIR sensitizer, indocyanine green (ICG), were effectively incorporated into the SCL micelles during the crosslinking reaction. The DOX/ICG-loaded SCL micelles showed pH- and NIR-responsive drug release, where burst release was observed under NIR laser irradiation. The in vitro cytotoxicity analysis demonstrated that the SCL was not cytotoxic against normal HFF-1 cells, while DOX/ICG-loaded SCL micelles exhibited significant antitumor activity toward HeLa cells. Thus, the SCL micelles of PLA20-b-P(FMA10-co-NAM78) can be used as a potential delivery vehicle for the controlled drug release in cancer therapy.

Polyurethane Foam Incorporated with Nanosized Copper-Based Metal-Organic Framework: Its Antibacterial Properties and Biocompatibility

Polyurethane foams (PUFs) have attracted attention as biomaterials because of their low adhesion to the wound area and suitability as biodegradable or bioactive materials. The composition of the building blocks for PUFs can be controlled with additives, which provide excellent anti-drug resistance and biocompatibility. Herein, nanosized Cu-BTC (copper(II)-benzene-1,3,5-tricarboxylate) was incorporated into a PUF via the crosslinking reaction of castor oil and chitosan with toluene-2,4-diisocyanate, to enhance therapeutic efficiency through the modification of the surface of PUF. The physical and thermal properties of the nanosized Cu-BTC-incorporated PUF (PUF@Cu-BTC), e.g., swelling ratio, phase transition, thermal gravity loss, and cell morphology, were compared with those of the control PUF. The bactericidal activities of PUF@Cu-BTC and control PUF were evaluated against Pseudomonas aeruginosa, Klebsiella pneumoniae, and methicillin-resistant Staphylococcus aureus. PUF@Cu-BTC exhibited selective and significant antibacterial activity toward the tested bacteria and lower cytotoxicity for mouse embryonic fibroblasts compared with the control PUF at a dose of 2 mg mL−1. The Cu(II) ions release test showed that PUF@Cu-BTC was stable in phosphate buffered saline (PBS) for 24 h. The selective bactericidal activity and low cytotoxicity of PUF@Cu-BTC ensure it is a candidate for therapeutic applications for the drug delivery, treatment of skin disease, and wound healing.

PEDOT:PSS-Modified Cotton Conductive Thread for Mass Manufacturing of Textile-Based Electrical Wearable Sensors by Computerized Embroidery

The textile industry has advanced processes that allow computerized manufacturing of garments at large volumes with precise visual patterns. The industry, however, is not able to mass fabricate clothes with seamlessly integrated wearable sensors, using its precise methods of fabrication (such as computerized embroidery). This is due to the lack of conductive threads compatible with standard manufacturing methods used in industry. In this work, we report a low-cost poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-modified cotton conductive thread (PECOTEX) that is compatible with computerized embroidery. The PECOTEX was produced using a crosslinking reaction between PEDOT:PSS and cotton thread using divinyl sulfone as the crosslinker. We extensively characterized and optimized our formulations to create a mechanically robust conductive thread that can be produced in large quantities in a roll-to-roll fashion. Using PECOTEX and a domestic computerized embroidery machine, we produced a series of wearable electrical sensors including a facemask for monitoring breathing, a t-shirt for monitoring heart activity and textile-based gas sensors for monitoring ammonia as technology demonstrators. PECOTEX has the potential to enable mass manufacturing of new classes of low-cost wearable sensors integrated into everyday clothes.