Surface Chemistry in Environmental Degradation of Polymeric Solids.

Microplastics (MPs) cause significant adverse environmental effects. To address this issue, a scientific approach for understanding the formation of MPs is essential. In this Perspective, we summarize the three typical degradation behaviors of polymeric solids from a surface chemistry perspective: chemical degradation, biodegradation, and mechanical degradation. These three degradation processes can occur consecutively or simultaneously in poorly managed polymeric materials, ultimately resulting in their disintegration into the environment. This Perspective provides valuable insights into controlling the degradation of polymeric solids and designing eco-friendly polymers for a sustainable future.

Controlling Microstructure-Transport Interplay in Poly(ether-block-amide) Multiblock Copolymer Gas Separation Membranes.

In this study, we investigated the effect of morphology on the gas-transport properties of a poly(ether-block-amide) (PEBA) multiblock copolymer. We annealed the copolymer samples and varied the annealing temperature to evaluate the influence of changes in the microstructure on the gas transport properties of PEBA. In addition, we used time-resolved attenuated total reflection Fourier transform infrared spectroscopy to evaluate the diffusion coefficient of CO2 in PEBA based on the Fickian model. The effect of the annealing temperature on the microphase-separated structure of the multiblock copolymer is discussed in detail. Furthermore, the gas diffusivity was significantly affected by the purity of the soft domains. The annealed sample demonstrated a 38% increase in CO2 permeability while maintaining a high CO2/N2 permselectivity of approximately 53. The findings of this study provide valuable insight into the design and optimization of PEBA membranes for gas separation applications.

Promotion of glyoxylic acid penetration into human hair by glycolic acid.

OBJECTIVE: Glyoxylic acid (GA) is widely used as a straight perming agent for hair care products, however, advanced GA penetration-enhancing agents are desired due to the peculiar odour and hair colour fading caused by the continuous use of GA products. Hence, it is important to develop a penetration-enhancing agent that helps minimize the GA concentration. We have found that the combined use of GA and glycolic acid (GCA) has a strong hair straightening effect. METHODS: Straightening hair test was carried out to the evaluation of the effect of additives. Liquid chromatography-mass spectrometry (LC/MS) was performed to quantify the GA penetration amount into human hair. Attenuated total reflection (ATR) Fourier transform-infrared spectroscopy (FT-IR) and FT-IR microscope were implemented to estimate the localization of GA in the hair. RESULTS: Straightening hair tests indicated that the hair straightening effect by GA was enhanced by the presence of GCA. LC/MS results showed that the addition of GCA enhanced the amount of GA that penetrated human hair by about four times. ATR FT-IR and FT-IR microscope measurements indicated that GA was localized more in the innermost region of hair (medulla) than the cortex and cuticle. The GA accumulated in the medulla disappeared after a hair straightener treatment at 180°C due to the chemical reaction. CONCLUSIONS: The GA penetration-enhancing effect of GCA is worth investigating to reduce the GA concentration in products for more comfortable use.

OBJECTIF: L'acide glyoxylique (AG) est largement utilisé en tant qu'agent de lissage pour les produits de soins capillaires. Cependant, des agents avancés améliorant la pénétration de l'AG sont souhaités en raison de l'odeur particulière et de la décoloration des cheveux causées par l'utilisation continue de produits à base d'AG. Il est donc important de mettre au point un agent améliorant la pénétration qui contribue à minimiser la concentration d'AG. Nous avons constaté que l'utilisation combinée de l'AG et de l'acide glycolique (AGC) a un fort effet lissant sur les cheveux. MÉTHODES: Un test de lissage des cheveux a été effectué pour évaluer l'effet des additifs. Une chromatographie en phase liquide avec spectrométrie de masse (liquid chromatography-mass spectrometry, LC/MS) a été réalisée pour quantifier le volume de pénétration de l'AG dans les cheveux humains. Une spectroscopie infrarouge à transformée de Fourier (Fourier transform-infrared spectroscopy, FT-IR) à réflexion totale atténuée (RTA) et un microscope FT-IR ont été adoptés pour estimer la localisation de l'AG dans les cheveux. RÉSULTATS: Les tests de lissage des cheveux ont indiqué que l'effet de lissage des cheveux de l'AG était renforcé par la présence d'AGC. Les résultats de la LC/MS ont montré que l'ajout d'AGC augmentait d'environ quatre fois la quantité d'AG pénétrant dans les cheveux humains. Les mesures de la FT-IR à RTA et du microscope FT-IR ont indiqué que l'AG était plus localisé dans la région la plus interne du cheveu (médulla) que dans le cortex et la cuticule. L'AG accumulé dans la médulla a disparu après un traitement au lisseur à cheveux à 180 °C en raison de la réaction chimique. CONCLUSIONS: L'effet d'amélioration de la pénétration de l'AG observé avec l'AGC mérite d'être étudié afin de réduire la concentration d'AG dans les produits pour une utilisation plus confortable.

Circular Polarization Luminescence of Groove Anchor Driving Optically Active Poly(methyl methacrylate) Stereocomplexes.

This paper presents a facile method for fabricating a thin-film sample with a high asymmetry value of induced circularly polarized luminescence (iCPL) (|glum| = 2.0 × 10-3). The method involves mixing stereoregular poly(methyl methacrylate) (PMMA) and chiral chromophore (2,2,2-trifluoro-1-(9-anthryl)ethanol (TFAE)) to form a complex with a dynamic helical conformation of poly(methyl methacrylate) (PMMA) associated with TFAE via hydrogen bonding. This dynamic helical conformation can be stabilized by the stereocomplexation of a pair of stereoregular PMMA, where the TFAE is sandwiched between a double-helix isotactic PMMA and single-helix syndiotactic PMMA, resulting in a preferential one-handed helical conformation with a high value of iCPL from self-assembly.

Neutron Reflectometry & Simultaneous Measurements of Rheology and Small Angle Neutron Scattering Studies for Polyether Modified Silicone Vesicle Systems.

Polyethyleneglycol 12 mol / polydimethylsiloxane co-polymer (PEG-12 dimethicone) is a type of polyether modified silicone (PEMS), which can form a lamellar liquid crystalline phase, and is widely used in cosmetics. The structural changes of PEG-12 dimethicone caused by water contents as well as shear flow were evaluated using simultaneous measurements of rheology and small angle neutron scattering (Rheo-SANS) and neutron reflectometry (NR). At high PEG-12 dimethicone concentrations (≥ 36 wt%), a reorientation of plate-like lamellar structures were observed and the neutral orientation was the most favorable. However, lamella-to-vesicle transitions were hardly observed. PEG-12 dimethicone turned out to form a bi-layer on a hydrophilized Si-wafer in a similar manner to that in bulk though the structure had a certain level of roughness.

Control cell migration by engineering integrin ligand assembly.

Advances in mechanistic understanding of integrin-mediated adhesion highlight the importance of precise control of ligand presentation in directing cell migration. Top-down nanopatterning limited the spatial presentation to sub-micron placing restrictions on both fundamental study and biomedical applications. To break the constraint, here we propose a bottom-up nanofabrication strategy to enhance the spatial resolution to the molecular level using simple formulation that is applicable as treatment agent. Via self-assembly and co-assembly, precise control of ligand presentation is succeeded by varying the proportions of assembling ligand and nonfunctional peptide. Assembled nanofilaments fulfill multi-functions exerting enhancement to suppression effect on cell migration with tunable amplitudes. Self-assembled nanofilaments possessing by far the highest ligand density prevent integrin/actin disassembly at cell rear, which expands the perspective of ligand-density-dependent-modulation, revealing valuable inputs to therapeutic innovations in tumor metastasis.

Specific deformation behavior of isotactic polypropylene films under a multiaxial stress field.

The specific deformation behavior of crystalline polymer films, namely unoriented crystallized isotactic polypropylene (it PP) films, was investigated under a multiaxial stress field. Changes in the aggregation structure of the films were investigated during the bulge deformation process using in situ small-angle X-ray scattering, wide-angle X-ray diffraction (WAXD) measurements, and polarized high-speed-camera observations. The films had a thickness of approximately 10 µm. The it PP films were fixed at the hole of a plate, then bulge deformation was applied using N2 or He gas pressure, and stress-strain curves were then calculated from the applied pressure and bulge height. Yielding was observed in the stress-strain curves. Below the yield point, in situ WAXD measurements revealed that the crystal lattice expanded isotropically at the center, edge, and bottom of the bulge hole. Above the yield point, a craze started to form slightly near the center, and crazes formed in various directions with a further increase in strain, while the crystal lattice expanded uniaxially along the circumference at the edge and bottom. Crazes oriented in various directions merged and lost birefringence, indicating a change to the isotropic orientation. The different directions of the crazes indicated several directions of stress. In other words, even if multiaxial deformation is applied to a crystalline it PP film, the string-shaped crystalline polymer chain structure produces local anisotropic uniaxial stress.

Critical In-Plane Density of Polyelectrolyte Brush for the Ordered Hydrogen-Bonded Structure of Incorporated Water.

A polymer electrolyte brush is a reasonable platform to confine water molecules within a nanoscopic area to study their role in the function of interacting media because of their adjustable nanospace and charge by changing the in-plane density and side chains of the brush. Here, we demonstrate how the in-plane spacing of cationic polymer brush chains, poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMTAC), affects the hydrogen bond configuration of incorporated water using soft X-ray emission spectroscopy. At the critical in-plane density σ = 0.30 chains/nm2 of PMTAC, tetrahedrally coordinated water molecules started to melt into distorted or broken hydrogen-bonded configurations. Considering the charge on the quaternary ammonium cations, the electric field required to form a tetrahedrally coordinated hydrogen-bonded configuration was estimated as ∼500 kV cm-1 and is effective up to ∼1 nm from the surface of the polymer chain. These findings are useful for designing specific interface properties and the resultant surface function of polyelectrolyte-based materials.

Cononsolvency of Poly[2-(methacryloyloxy)ethyl phosphorylcholine] in Ethanol-Water Mixtures: A Neutron Reflectivity Study.

Molecular mechanisms underlying the cononsolvency, a re-entrant coil-to-globule-to-coil conformational transition of polymer chains in mixtures of two good solvents, of poly[2-(methacryloyloxy)ethyl phosphorylcholine] (PMPC) in ethanol-water binary mixtures were complementarily investigated. This was accomplished by following a statistical mechanical model for competitive hydrogen bonding combined with the cooperative solvation concept as well as neutron reflectivity (NR) experiments employing contrast variation in the cononsolvents. The experimental re-entrant aggregation of the PMPC chains in ethanol-water mixed solvents, obtained on the basis of turbidity was accurately reproduced by theoretical calculations. The calculation proved the relatively strong cooperativity of ethanol and the preferential interaction of water, while the total coverage of solvents was the lowest at an ethanol volume fraction (fethanol) of 0.90. At this level, the cononsolvency was the most significant, and the collapsed PMPC chains were solvated with more water than the bulk mixed solvent. The ethanol-water cononsolvency for the PMPC brushes on a planar silicon wafer was investigated by NR experiments, and the solvent composition involved in the collapsed PMPC brush was addressed according to the contrast variation study with mixed solvents of water, deuterium oxide, ethanol-d5, and ethanol-d6. The collapsed PMPC brushes at fethanol = 0.90 contained more water than the bulk solvent. The preferential distribution of water in the collapsed PMPC brush was consistent with the simulation results. Therefore, the molecular mechanism for the cononsolvency of PMPC in ethanol-water mixed solvents based on competitive hydrogen bonding coupled with cooperative solvation was experimentally rationalized.

Modulation of Double Zwitterionic Block Copolymer Aggregates by Zwitterion-Specific Interactions.

Transformable double hydrophilic block copolymer assemblies are valid as a biocompatible smart macromolecular system. The molecular mechanisms in the spontaneous assembly of double zwitterionic diblock copolymers composed of a poly(carboxybetaine methacrylate) (PCB2) and a poly(sulfobetaine methacrylate) (PSB4) chains (PCB2-b-PSB4) were investigated by the modulation of the aggregates in response to nondetergent zwitterions. The PCB2-b-PSB4 diblock copolymers with a high degree of polymerization PSB4 block produced aggregates in salt-free water through "zwitterion-specific" interactions. The PCB2-b-PSB4 aggregates were dissociated by the addition of nondetergent sulfobetaine (SB4) and carboxybetaine (CB2) molecules, while the aggregates showed different aggregation modulation processes for SB4 and CB2. Zwitterions with different charged groups from SB4 and CB2, glycine and taurine, hardly disrupted the PCB2-b-PSB4 aggregates. The PCB2-b-PSB4 aggregate modulation efficiency of SBs associated with the intercharge hydrocarbon spacer length (CSL) rather than the symmetry with the SB in the PSB chain. These zwitterion-specific modulation behaviors were rationalized based on the nature of zwitterions including partial charge density, dipole moment, and hydrophobic interactions depending on the charged groups and CSL.

Probing the in-plane liquid-like behavior of liquid crystal elastomers.

When isotropic solids are unequally stretched in two orthogonal directions, the true stress (force per actual cross-sectional area) in the larger strain direction is typically higher than that in the smaller one. We show that thiol-acrylate liquid crystal elastomers with polydomain texture exhibit an unusual tendency: The true stresses in the two directions are always identical and governed only by the area change in the loading plane, independently of the combination of imposed strains in the two directions. This feature proves a previously unidentified state of matter that can vary its shape freely with no extra mechanical energy like liquids when deformed in the plane. The theory and simulation that explain the unique behavior are also provided. The in-plane liquid-like behavior opens doors for manifold applications, including wrinkle-free membranes and adaptable materials.

Actuator Performance of Dielectric Elastomers Comprising Hydrogenated Carboxylated Acrylonitrile-Butadiene Rubber/Nitrile Group-Modified Titanium Oxide Particles.

We prepared a dielectric elastomer actuator composed of hydrogenated carboxylated acrylonitrile-butadiene rubber (HXNBR)/nitrile group (CN)-modified and non-modified titanium oxide (TiO2) particles with insulation properties. The CN group-containing silane coupling agent was synthesized via a thiol-ene reaction between acrylonitrile and 3-mercaptpropyltrimethoxysilane and immobilized onto the TiO2 particle surface. The HXNBR/CN-modified and non-modified TiO2 particle composite elastomer showed a high relative dielectric constant and generated stress in a low electric field. The relative dielectric constant increased proportionally with the amount of CN-modified TiO2 particles, showing a value of 22 at 100 Hz. As the dielectric constant increased, the volumetric resistivity decreased; however, the dielectric breakdown strength was maintained at 95 V/mm. The generated stress of the composite elastomer increased in proportion to the relative dielectric constant, showing a maximum of 1.9 MPa. The card-house structure of TiO2 particles in the composite elastomer is assumed to suppress the dielectric breakdown in a low electric field. Thus, we demonstrated that an elastomer containing a high dipole group on an insulating particle surface is capable of improving the power performance of soft actuators.

Exploring the Mesoscopic Morphology in Mussel Adhesive Proteins by Soft X-ray Spectromicroscopy.

Marine mussels efficiently adhere under wet conditions by precisely controlling the hierarchical structure of the adhesive plaque through sequential mussel foot protein secretion in the foot-tip cavity. Chemical analysis of the non-uniform mussel plaque morphology has been performed using spectromicroscopy; however, the mesoscopic morphology has not been elucidated yet because of the limited spatial resolution of conventional chemical imaging techniques. We investigated the chemical speciation in the non-uniform mussel plaque morphology employing scanning transmission soft X-ray spectromicroscopy (STXM). The high-spatial-resolution STXM chemical imaging with C 1s near-edge X-ray absorption fine structure yields the distribution of the hydroxy-substituted aromatic residues in the sub-micron scale non-uniform mussel plaque morphology. The matrix consists of a high-protein-density cured product containing a large number of hydroxy-substituted aromatic carbons, including tyrosine and 3,4-dihydroxyphenylalanine (Dopa), whereas the microdomains are poor-protein-density regions with a low aromatic residue relative content. The adhesive interface was covered with the matrix phase to ensure adhesion. The cuticle layer involves a moderate Dopa content, which appears to be optimized for the mechanical performance of the skin.

Actuator Performance of a Hydrogenated Carboxylated Acrylonitrile-Butadiene Rubber/Silica-Coated BaTiO3 Dielectric Elastomer.

We synthesized silica-coated barium titanate (BaTiO3) particles with different silica shell thicknesses and evaluated the effect of silica coating on the relative dielectric properties of silica-coated BaTiO3 particles. Furthermore, composite elastomers were prepared using hydrogenated carboxylated acrylonitrile-butadiene rubber (HXNBR) with a high relative dielectric constant (εr) and silica-coated BaTiO3 particles, and their performance as an actuator was evaluated. Both εr and relative dielectric loss of non-coated BaTiO3 particles increased at low frequencies (<200 Hz) associated with ionic conduction. However, εr and relative dielectric loss were reduced for the silica-coated BaTiO3 particles with thick silica shells, indicating that silica coating reduced ion migration. The dielectric breakdown strength increased with the thickness of the silica shell; it increased up to 80 V/µm for HXNBR/silica-coated BaTiO3 particles with 20 nm-thick silica shells. The maximum generated stress, strain, and output energy density of the composite elastomer with HXNBR (with a high relative constant) and silica-coated BaTiO3 were 1.0 MPa, 7.7%, and 19.4 kJ/m3, respectively. In contrast, the values of the same parameters for a reference elastomer (acrylic/BaTiO3; with low εr) were 0.4 MPa, 6.7%, and 6.8 kJ/m3 at the dielectric breakdown strength of 70 V/µm. The results indicated that the elastomers composed of HXNBR and silica-coated BaTiO3 exhibited higher generated stress, strain, and output energy density than elastomers for conventional dielectric actuators.

Preparation and characterization of an imogolite/chitosan hybrid with pyridoxal-5'-phosphate as an interfacial modifier.

Imogolite/chitosan hybrid films were prepared using pyridoxal-5'-phosphate (PLP) as an interfacial modifier. Thermogravimetric analysis and spectroscopic measurements revealed that the phosphate group of PLP was adsorbed on the imogolite. Furthermore, rheological measurements suggested that the PLP-modified imogolites (PLP-imogolite) had strong interactions with chitosan in solution. Moreover, UV absorption of the hybrid film showed that PLP and chitosan formed Schiff base linkages. Therefore, the hybrid films exhibited a significant improvement in their mechanical properties compared to those of pristine chitosan/imogolite hybrid films.

Complex Network Representation of the Structure-Mechanical Property Relationships in Elastomers with Heterogeneous Connectivity.

The complicated structure-property relationships of materials have recently been described using a methodology of data science that is recognized as the fourth paradigm in materials science. In network polymers or elastomers, the manner of connection of the polymer chains among the crosslinking points has a significant effect on the material properties. In this study, we quantitatively evaluate the structural heterogeneity of elastomers at the mesoscopic scale based on complex network, one of the methods used in data science, to describe the elastic properties. It was determined that a unified parameter with topological and spatial information universally describes some parameters related to the stresses. This approach enables us to uncover the role of individual crosslinking points for the stresses, even in complicated structures. Based on the data science, we anticipate that the structure-property relationships of heterogeneous materials can be interpretatively represented using this type of "white box" approach.

Relationship between the Relative Dielectric Constant and the Monomer Sequence of Acrylonitrile in Rubber.

Acrylonitrile-butadiene rubbers (NBRs) have a lower glass transition temperature (T g) and a higher dielectric constant than other rubbers. To understand how a low T g and a high dielectric constant are compatible, we focused on the acrylonitrile (AN) monomer sequence in rubber and synthesized random and alternating copolymers to evaluate the effect of the sequence. The AN monomer sequence dependence of the relative dielectric constant was investigated by the C-N stretching vibration of the nitrile group through Fourier transform infrared spectroscopy and internal rotation potential energy measurements around the C-C bond within the nitrile group based on dimer model calculations. The alternating copolymers, including NBR, showed a higher dielectric constant than random copolymers. The alternating copolymer shifted from ∼2243 cm-1 for polyAN to ∼2236 cm-1 for NBRs, while the random copolymer only shifted to ∼2239 cm-1. The peak of the C-N stretching vibration was correlated with the AN sequence. The sequence dependence of the shift can be explained by the C-N bond length calculation. The internal rotation potential energy between gauche and trans of the NBR model was the lowest, indicating that the NBR main chain is flexible and that AN in the main chain rotates easily. Therefore, NBR has a high dielectric constant and a low T g because of the presence of an alternating sequence and the flexibility of the NBR main chain.

Application of Synchrotron Radiation X-ray Scattering and Spectroscopy to Soft Matter.

Light produced by synchrotron radiation (SR) is much brighter than that produced by conventional laboratory X-ray sources. The photon energy of SR X-ray ranges from soft and tender X-rays to hard X-rays. Moreover, X-rays become element sensitive with decreasing photon energy. By using a wide energy range and high-quality light of SR, different scattering and spectroscopic methods were applied to various soft matters. We present five of our recent studies performed using specific light properties of a synchrotron facility, which are as follows: (1) In situ USAXS study to understand the deformation behavior of colloidal crystals during uniaxial stretching; (2) structure characterization of semiconducting polymer thin films along the film thickness direction by grazing-incidence wide-angle X-ray scattering using tender X-rays; (3) X-ray absorption fine structure (XAFS) analysis of the formation mechanism of poly(3-hexylthiophene) (P3HT); (4) soft X-ray absorption and emission spectroscopic analysis of water structure in polyelectrolyte brushes; and (5) X-ray photon correlation spectroscopic analysis of the diffusion behavior of polystyrene-grafted nanoparticles dispersed in a polystyrene matrix.