Refractive Index Engineering as a Novel Strategy toward Highly Transparent and Tough Sustainable Polymer Blends

Enhanced strength, toughness and heat resistance of poly (lactic acid) with good transparency and biodegradability by uniaxial pre-stretching

Sustainable poly (lactic acid) (PLA) with excellent strength, toughness, heat resistance, transparency, and biodegradability was achieved by uniaxial pre-stretching at 70 °C. The effect of pre-stretched ratio (PSR) on the microstructure and properties of the PLA was investigated. The undrawn PLA was brittle. However, after pre-stretching, the elongation at break was increased significantly. The maximum value of 161.2 % was obtained at pre-stretching ratio (PSR) of 1.0. With the increase of PSR, the modulus and strength were improved obviously (from 1601 MPa and 60.2 MPa for undrawn PLA to 2932 MPa and 106.3 MPa for the ps-PLA at PSR =3.0). Meanwhile, the heat resistance of PLA was improved obviously with the increase of PSR. For the ps-PLA3.0, there were almost no deformation and shrink at 140 °C. Interestingly, after pre-stretching, the PLA still maintained the good transparency and biodegradability. The brittleness for undrawn PLA was attributed to the network structure of cohesional entanglements. After pre-stretching, the destruction of the network structure and formation of the orientation, mesophase and oriented nanosized crystalline phase lead to the increased the toughness, strength and heat resistance without sacrificing the transparency and biodegradability. This work provides a significant guidance for the fabrication of PLA material with excellent comprehensive performance including strength, toughness, heat resistance, transparency, and biodegradability.

Polymeric Nanozyme with SOD Activity Capable of Inhibiting Self- and Metal-Induced α-Synuclein Aggregation

Despite decades of research, Parkinson's disease is still an idiopathic pathology for which no cure has yet been found. This is partly explained by the multifactorial character of most neurodegenerative syndromes, whose generation involves multiple pathogenic factors. In Parkinson's disease, two of the most important ones are the aggregation of α-synuclein and oxidative stress. In this work, we address both issues by synthesizing a multifunctional nanozyme based on grafting a pyridinophane ligand that can strongly coordinate CuII, onto biodegradable PEGylated polyester nanoparticles. The resulting nanozyme exhibits remarkable superoxide dismutase activity together with the ability to inhibit the self-induced aggregation of α-synuclein into amyloid-type fibrils. Furthermore, the combination of the chelator and the polymer produces a cooperative effect whereby the resulting nanozyme can also halve CuII-induced α-synuclein aggregation.

A biomechanical study of a polymer material bundled rib fracture fixator

BACKGROUND

Rib fractures are one of the most common blunt injuries, accounting for approximately 10% of all trauma patients and 60% of thoracic injuries. Multiple rib fractures, especially flail chest, can cause local chest wall softening due to the loss of rib support, leading to paradoxical breathing, severe pain, and a high likelihood of accompanying lung contusions.

OBJECTIVE

This study investigates the mechanical properties of a new polymer material rib internal fixator to provide theoretical data for its clinical use.

METHODS

We conducted in vitro mechanical tests on 20 fresh caudal fin sheep ribs, using different fracture models across four randomly assigned groups (five ribs per group). The fixators were assessed using non-destructive three-point bending, torsion, and unilateral compression tests, with results averaged. Additionally, finite element analysis compared stress and strain in the polymer fixators and titanium alloy rib plates during bending and torsion tests.

RESULTS

In vitro tests showed that the polymer fixators handled loads effectively up to a maximum without increase beyond a certain displacement. Bending and torsion tests via finite element analysis showed the polymer material sustained lower maximum equivalent stresses (84.455 MPa and 14.426 MPa) compared to titanium alloy plates (219.88 MPa and 46.47 MPa).

CONCLUSION

The polymer rib fixator demonstrated sufficient strength for rib fracture fixation and was superior in stress management compared to titanium alloy plates in both bending and torsion tests, supporting its potential clinical application.

Metal-catalyzed copolymerizations of epoxides and carbon disulfide for high-refractive index low absorbance adhesives and plastics

High-refractive index plastics are useful materials due to their optical properties, ease of processing, and low-costs compared to their inorganic counterparts. Catalytic carbon disulfide (CS2) copolymerization with epoxides is one method for producing low-cost high refractive index polymers. The reaction is accompanied by an oxygen-sulfur exchange reaction which produces irregular microstructures in the repeating units. In this study, metal salen catalysts were investigated with different metal centers (Al, Cr, Co) and salen ligand electronics, sterics, backbones, and co-catalyst in the copolymerization of CS2 with propylene oxide (PO) and cyclohexene oxide (CHO). The results reveal the essential nature of Cr metal centers on reactivity and the backbone geometry on monomer selectivity. There were no significant impacts on the O-S exchange reaction when ligand design changed, however PO and CHO/CS2 copolymers yield different monothiocarbonate microstructures. Additionally, the effects of microstructure on optical and thermal properties were investigated using spectroscopic ellipsometry and calorimetry, respectively. The CHO system produced high T g plastics (93°C) with high refractive indexes (n up to 1.64), modest absorbance (κ < 0.020), and Abbe numbers of 32.2 while PO yielded low T g adhesives (T g = 9°C) with high refractive indexes (n up to 1.73), low absorbance (κ < 0.005), and low Abbe numbers (V D = 19.1).

Modification of polylactide by poly(ionic liquid)-b-polylactide copolymer and bio-based ionomers: Excellent toughness, transparency and antibacterial property

Polylactide (PLA) is one of the most attractive bioplastics as it can be produced from nontoxic renewable feedstock. However, its inherently poor toughness greatly limits its large-scale application. Cost-effectively toughening PLA without sacrificing its transparency remains a big challenge. We herein prepared an imidazolium-based poly(ionic liquid)-b-PLA copolymer (ILA) and ionomers as toughening agent for PLA through an integrative approach including continuous-monomer-feeding copolymerization, quaternization reaction, ion exchange and inter-ionomers blending. By blending PLA with the ILA and ionomers, we successfully obtained PLA materials with combined features including high toughness, good transparency and antibacterial properties. The effects of regulated ionomer composition and ILA compatibilizer on phase morphology, mechanical properties and transparency of the blends were systematically studied. The optimum formulation (PLA/E12/ILA 60/40/5) shows an impressive transmittance of 89-93 %, high impact strength of 45 kJ/m² and elongation at break at 170 %, which are about 17 and 24 times that of pure PLA, respectively. More interestingly, the presence of imidazolium cation and anion groups endows the blends with attractive antibacterial properties. Ion exchange between ILA copolymer and the imidazolium-containing ionomeric system leads to a synergistic effect of compatibilization and efficient toughening, providing a new strategy for develop high performance PLA materials.

Ultra-Tough Polylactide/Bromobutyl Rubber-Based Ionomer Blends via Reactive Blending Strategy

A series of ultra-toughened sustainable blends were prepared from poly(lactic acid) (PLA) and bromobutyl rubber-based ionomers (i-BIIRs) via reactive blending, in which dicumyl peroxide (DCP) and Joncryl®ADR-4440 (ADR) were used as reactive blending additives. The miscibility, phase morphology and mechanical property of the PLA/i-BIIRs blends were thoroughly investigated through DMA, SEM, tensile and impact tests. The influence of different ionic groups and the effects of DCP and ADR on the compatibility between the phases, phase structure and mechanical properties were analyzed. The introduction of the imidazolium-based ionic groups and the reactive agents enable the i-BIIRs play multiple roles as effective compatibilizers and toughening agents, leading to improved interfacial compatibility and high toughness of the blends. The mechanical properties test showed that the PLA/i-BIIRs blends exhibit excellent toughness: impact strength and the elongation at break of AR-OH(30)+AD reached 95 kJ/m² and 286%, respectively. The impact fracture surface showed the large-scale plastic deformation of the PLA matrix in the blends, resulting in greatly absorbing the impact energy. The results proved that simultaneously applying reactive blend and multiple intermolecular interactions methods is an effective toughening strategy for toughening modification of the PLA blends.

Transparent Fiber-Reinforced Composites Based on a Thermoset Resin Using Liquid Composite Molding (LCM) Techniques

In this study, optically transparent glass fiber-reinforced polymers (tGFRPs) were produced using a thermoset matrix and an E-glass fabric. In situ polymerization was combined with liquid composite molding (LCM) techniques both in a resin transfer molding (RTM) mold and a lite-RTM (L-RTM) setup between two glass plates. The RTM specimens were used for mechanical characterization while the L-RTM samples were used for transmittance measurements. Optimization in terms of the number of glass fabric layers, the overall degree of transparency of the composite, and the mechanical properties was carried out and allowed for the realization of high mechanical strength and high-transparency tGFRPs. An outstanding degree of infiltration was achieved maintaining up to 75% transmittance even when using 29 layers of E-glass fabric, corresponding to 50 v.% fiber, using an L-RTM setup. RTM specimens with 44 v.% fiber yielded a tensile strength of 435.2 ± 17.6 MPa, and an E-Modulus of 24.3 ± 0.7 GPa.