ACS polymers Au最新文献

Thermoset polymers serve a significant role in modern industrial applications, and with a global annual output of over 65 million tons to meet this growing demand for sustainable materials, scientists and engineers need to go beyond what makes a material best for a certain use. Vinyl ester (VE) is a thermosetting polymer derived from polyester and epoxy resin. Its mixing properties distinguish it from its competitors, offering advantages in terms of curing efficiency, wettability, corrosion resistance, and low cost, which are crucial for modern industrial applications. Researchers have continuously explored the modifications of the intrinsic properties of VE using additives to enhance its flame retardancy and mechanical characteristics for more cost-effective and environmentally friendly materials applicable across various industries. In this study, we developed an easy-to-process eco-thermoset blend additive (50% v/v), known as maleated epoxidized corn oil/epoxy resin (MEPECO). Adding an optimal amount of MEPECO (5%) to the VE resin significantly improved its flame retardancy properties, as assessed by pyrolysis-combustion flow calorimetry, contact angle measurements, and thermogravimetric analysis. The mechanical properties, specifically strength, also showed substantial enhancement with the same optimal amount of MEPECO, as determined by flexural testing and spectral analysis. However, during the digestion of the eco-thermoset resin, the modulus and impact energy were notably lower owing to shear-yielding localization, as evidenced by the morphological analysis. This paper presents a novel in situ and straightforward technique for the easy and effective blending of eco-thermoset additives into petroleum-based epoxy resins, thereby facilitating their potential application in the development of sustainable green composite materials.

Thermoset polymers serve a significant role in modern industrial applications, and with a global annual output of over 65 million tons to meet this growing demand for sustainable materials, scientists and engineers need to go beyond what makes a material best for a certain use. Vinyl ester (VE) is a thermosetting polymer derived from polyester and epoxy resin. Its mixing properties distinguish it from its competitors, offering advantages in terms of curing efficiency, wettability, corrosion resistance, and low cost, which are crucial for modern industrial applications. Researchers have continuously explored the modifications of the intrinsic properties of VE using additives to enhance its flame retardancy and mechanical characteristics for more cost-effective and environmentally friendly materials applicable across various industries. In this study, we developed an easy-to-process eco-thermoset blend additive (50% v/v), known as maleated epoxidized corn oil/epoxy resin (MEPECO). Adding an optimal amount of MEPECO (5%) to the VE resin significantly improved its flame retardancy properties, as assessed by pyrolysis-combustion flow calorimetry, contact angle measurements, and thermogravimetric analysis. The mechanical properties, specifically strength, also showed substantial enhancement with the same optimal amount of MEPECO, as determined by flexural testing and spectral analysis. However, during the digestion of the eco-thermoset resin, the modulus and impact energy were notably lower owing to shear-yielding localization, as evidenced by the morphological analysis. This paper presents a novel in situ and straightforward technique for the easy and effective blending of eco-thermoset additives into petroleum-based epoxy resins, thereby facilitating their potential application in the development of sustainable green composite materials.

Application of protective polymer coatings to enhance the biostability of DNA-based nanomaterials (DONs) has become common practice in in vitro and in vivo experiments. While the functional effect of these coatings is obvious, a detailed molecular picture of what is protected and for how long remains unclear. Additionally, the use of the oligolysine-1kPEG protective polymer has been limited due to aggregation issues. In this study, we evaluated the colloidal stability, structural integrity, and functional preservation of DONs coated with oligolysine (K)-1k/5kPEG block copolymers. Dynamic light scattering and transmission electron microscopy were employed to assess colloidal stability before and after degradation. A FRET-based assay was developed to monitor the directionality of degradation, while quantitative PCR measured the protection of functional DNA handles, crucial for the design of ligand-functionalized DONs. Our results show that K₁₀-1kPEG, while prone to aggregation, can offer similar protection against nucleases as K₁₀-5kPEG, provided buffer conditions are carefully chosen. Maintaining the colloidal, structural, and functional stability before and after nuclease exposure supports DON applications, particularly at the biointerface. These insights provide valuable guidelines for selecting the most effective protection strategy and enhancing DON functionality across diverse biological environments.

Application of protective polymer coatings to enhance the biostability of DNA-based nanomaterials (DONs) has become common practice in in vitro and in vivo experiments. While the functional effect of these coatings is obvious, a detailed molecular picture of what is protected and for how long remains unclear. Additionally, the use of the oligolysine-1kPEG protective polymer has been limited due to aggregation issues. In this study, we evaluated the colloidal stability, structural integrity, and functional preservation of DONs coated with oligolysine (K)-1k/5kPEG block copolymers. Dynamic light scattering and transmission electron microscopy were employed to assess colloidal stability before and after degradation. A FRET-based assay was developed to monitor the directionality of degradation, while quantitative PCR measured the protection of functional DNA handles, crucial for the design of ligand-functionalized DONs. Our results show that K₁₀-1kPEG, while prone to aggregation, can offer similar protection against nucleases as K₁₀-5kPEG, provided buffer conditions are carefully chosen. Maintaining the colloidal, structural, and functional stability before and after nuclease exposure supports DON applications, particularly at the biointerface. These insights provide valuable guidelines for selecting the most effective protection strategy and enhancing DON functionality across diverse biological environments.

Chemoenzymatic polymerization (CEP) using enzymes as catalysts is gaining attention as an environmentally friendly method for synthesizing polypeptides. This method proceeds under mild conditions in aqueous solvents and leverages the substrate specificity of enzymes, allowing polymerization reactions to occur without the need to protect reactive side-chain functional groups. However, the monomers used must have esterified C-termini, such as amino acids or oligopeptides. In this study, we used l-lysine (Lys-OH) as a model example and performed one-pot CEP with papain without isolating the esterified lysine. Esterification of Lys-OH was achieved by using hydrochloric acid as a catalyst in ethanol, and one-pot polymerization resulted in poly-l-lysine (polyLys) with a peak top degree of polymerization (DP) of 6 and a maximum DP of 18, with a 31% conversion from the nonesterified lysine. The obtained polyLys was all α-linked, demonstrating that regioselective polymerization was successfully achieved even with one-pot CEP.

Chemoenzymatic polymerization (CEP) using enzymes as catalysts is gaining attention as an environmentally friendly method for synthesizing polypeptides. This method proceeds under mild conditions in aqueous solvents and leverages the substrate specificity of enzymes, allowing polymerization reactions to occur without the need to protect reactive side-chain functional groups. However, the monomers used must have esterified C-termini, such as amino acids or oligopeptides. In this study, we used l-lysine (Lys-OH) as a model example and performed one-pot CEP with papain without isolating the esterified lysine. Esterification of Lys-OH was achieved by using hydrochloric acid as a catalyst in ethanol, and one-pot polymerization resulted in poly-l-lysine (polyLys) with a peak top degree of polymerization (DP) of 6 and a maximum DP of 18, with a 31% conversion from the nonesterified lysine. The obtained polyLys was all α-linked, demonstrating that regioselective polymerization was successfully achieved even with one-pot CEP.

Polymer-blend-based nanocomposites incorporating carbon nanomaterials hold significant potential for microwave absorption materials (MAM) applications. This study investigates the microwave absorption response of hybrid nanocomposites composed of multiwalled carbon nanotubes (MWCNT) and nanographite, prepared using industrial-like melt-mixing masterbatch strategies in a polycarbonate/acrylonitrile-butadiene-styrene copolymer (PC/ABS) blend matrix with varying blend ratios (100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100) and a constant filler content (2 wt % MWCNT and 2 wt % nanographite). Furthermore, the PC/ABS (40/60) blend-based nanocomposite was prepared with the addition of a compatibilizer, 5 wt % of maleic anhydride grafted ABS (ABS-g-MAH), to verify possible changes in morphology. Morphology, rheology, mechanical, electrical, and electromagnetic properties were correlated. From a morphological perspective, a preferential distribution of MWCNTs within the PC phase was observed, with the different blend ratios leading to a transition from a dispersed matrix morphology in 80/20 and 20/80 (PC/ABS) to cocontinuous morphologies in the intermediate blends (60/40, 50/50, and 40/60). The addition of ABS-g-MAH as a compatibilizer resulted in significant morphological refinement. Electromagnetic properties, evaluated using both X-band rectangular waveguide and broadband coaxial airline techniques, as well as electrical conductivity, were found to be strongly influenced by the varying morphologies. The nanocomposite PC/ABS/ABS-g-MAH with a thickness of 3.0 mm presented a Reflection Loss (RL) of −29.4 dB at 9.44 GHz, with a bandwidth of 3 GHz. Across the broadband spectrum, RL values below −10 dB were observed, including at lower frequencies around 3.70 GHz. These findings suggest that morphological tuning of the polymer matrix offers a promising pathway for optimizing microwave absorption in hybrid nanocomposites.

Polymer-blend-based nanocomposites incorporating carbon nanomaterials hold significant potential for microwave absorption materials (MAM) applications. This study investigates the microwave absorption response of hybrid nanocomposites composed of multiwalled carbon nanotubes (MWCNT) and nanographite, prepared using industrial-like melt-mixing masterbatch strategies in a polycarbonate/acrylonitrile-butadiene-styrene copolymer (PC/ABS) blend matrix with varying blend ratios (100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100) and a constant filler content (2 wt % MWCNT and 2 wt % nanographite). Furthermore, the PC/ABS (40/60) blend-based nanocomposite was prepared with the addition of a compatibilizer, 5 wt % of maleic anhydride grafted ABS (ABS-g-MAH), to verify possible changes in morphology. Morphology, rheology, mechanical, electrical, and electromagnetic properties were correlated. From a morphological perspective, a preferential distribution of MWCNTs within the PC phase was observed, with the different blend ratios leading to a transition from a dispersed matrix morphology in 80/20 and 20/80 (PC/ABS) to cocontinuous morphologies in the intermediate blends (60/40, 50/50, and 40/60). The addition of ABS-g-MAH as a compatibilizer resulted in significant morphological refinement. Electromagnetic properties, evaluated using both X-band rectangular waveguide and broadband coaxial airline techniques, as well as electrical conductivity, were found to be strongly influenced by the varying morphologies. The nanocomposite PC/ABS/ABS-g-MAH with a thickness of 3.0 mm presented a Reflection Loss (RL) of -29.4 dB at 9.44 GHz, with a bandwidth of 3 GHz. Across the broadband spectrum, RL values below -10 dB were observed, including at lower frequencies around 3.70 GHz. These findings suggest that morphological tuning of the polymer matrix offers a promising pathway for optimizing microwave absorption in hybrid nanocomposites.

Programmable synthesis of polymer nanoparticles prepared by polymerization-induced self-assembly (PISA) mediated by reversible addition-fragmentation chain-transfer (RAFT) dispersion polymerization with specified diameter is achieved in an automated flow-reactor platform. Real-time particle size and monomer conversion is obtained via inline spatially resolved dynamic light scattering (SRDLS) and benchtop nuclear magnetic resonance (NMR) instrumentation. An initial training experiment generated a relationship between copolymer block length and particle size for the synthesis of poly(N,N-dimethylacrylamide)-b-poly(diacetone acrylamide) (PDMAm-b-PDAAm) nanoparticles. The training data was used to target the product compositions required for synthesis of nanoparticles with defined diameters of 50, 60, 70, and 80 nm, while inline NMR spectroscopy enabled rapid acquisition of kinetic data to support their scale-up. NMR and SRDLS were used during the continuous manufacture of the targeted products to monitor product consistency while an automated sampling system collected practically useful quantities of the targeted products, thus outlining the potential of the platform as a tool for discovery, development, and manufacture of polymeric nanoparticles.

Itaconates available from renewable resources constitute a group of monomers that are used in several types of polymerizations. Their use in free-radical polymerizations (FRPs) is still limited due to the low propagation rate coefficients resulting in low polymerization rates and the occurrence of depropagation which is responsible for limited monomer conversion. Since FRP is considered very robust with few requirements concerning monomer purity, it is still interesting to investigate how itaconate FRP may become feasible. For this reason, copolymerizations of itaconates with other monomers well-suited for FRP are considered. In particular, copolymerization with acrylates appears to be interesting because the propagation rate of these monomers is high and depropagation is not operative at common polymerization temperatures. Copolymerizations of dibutyl and dicyclohexyl itaconate with butyl acrylate were performed to determine the copolymerization reactivity ratios required for tailoring copolymer composition. To limit the number of experiments, copolymerizations were carried out until high conversion and consumption of the individual monomers was obtained from ¹H NMR spectroscopy and quantitative size-exclusion chromatography.