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Comb-like polymers with pendant-like perfluorocarbon side chains self-assemble into smectic lamellae and have been extensively used as water-repellent, hydrophobic coating materials characterized by large water contact angles (θ > 120°). As poly(perfluorooctyl acrylate) films are “apparently hydrophobic” (θ > 120°), the interaction of such materials and water molecules has been largely overlooked. To unravel the molecular-level interactions between water and apparently hydrophobic polymers, specular and off-specular neutron scattering experiments were conducted at defined osmotic pressure ΠH2O. The poly{2-[(perfluorooctylethyl)carbamate]ethyl} acrylate (PFAUr-C8), which had a carbamate linker, transitioned to another lamellar phase at 89 °C. At T = 25 °C; the lamellar periodicity of PFAUr-C8 slightly increased with decreasing osmotic pressure, while the vertical correlation length increased. However, the poly[(perfluorooctyl)ethyl] acrylate (PFA-C8) that did not contain a carbamate linker directly transitioned to a disordered phase at 84 °C. The lamellar periodicity of PFA-C8 was largely independent of the osmotic pressure, suggesting that PFA-C8 was poorly hydrated. Remarkably, the vertical correlation length decreased with decreasing osmotic pressure. Because hydration facilitated by the linker modulated the smectic lamellae of the poly(perfluoroalkyl acrylate), water molecules could be used to optimize the self-assembly of apparently hydrophobic liquid crystalline polymers. Self-assembled smectic lamellae of comb-like polymers with pendant-like perfluorocarbon side chains have been extensively used as water-repellent, hydrophobic coating materials, which are characterized by large water contact angles (θ > 120°). By measuring off-specular neutron scattering under defined osmotic pressures, we unraveled that such “apparently hydrophobic” materials interact with water and adapt the inter-lamellar correlation. This suggested that water molecules could be used to optimize the self-assembly of hydrophobic liquid crystalline polymers.

The terpolymerization of a non-polar olefin (such as ethylene) and two different polar functional olefins in a controlled fashion is of great interest and importance but has hardly been explored to date. We report for the first time the terpolymerization of ethylene (E) and two different methoxyaryl-substituted propylenes (AR1 P=hexylanisyl propylene; AR2 P=methoxynaphthyl propylene or methoxypyrenyl propylene) by a half-sandwich scandium catalyst. The terpolymerization took place in a sequence-controlled fashion, affording unique multi-block copolymers composed of two different ethylene-alt-methoxyarylpropylene sequences E-alt-AR1 P (soft segments) and E-alt-AR2 P (hard segments) and relatively short ethylene-ethylene (EE) blocks (crystalline segments). The terpolymers exhibited excellent elasticity and unprecedented self-healing as a result of microphase separation of nanodomains of the crystalline EE segments and the hard amorphous E-alt-AR2 P segments from a very flexible E-alt-AR1 P matrix, demonstrating unique synergy of the three different components.

High-density poly(α-methylene-γ-butyrolactone) (PMBL) brushes were produced by surface-initiated atom transfer radical polymerization of α-methylene-γ-butyrolactone (MBL), a biomass derived from tulips, on a silicon substrate. The relative elastic modulus was evaluated through force-curve measurements using a scanning force microscopy. The friction coefficient was measured using a macroscopic friction test. The PMBL brushes exhibit larger elastic modulus and better friction resistance than PMMA brushes as a result of the highly stretched conformation and polar interaction between PMBL chains.

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.

Nanocomposites composed of monodisperse silica nanoparticles (SiNPs) modified with an elastic comb-shaped block copolymer brush were produced for the first time. Comb-shaped polymer brushes consisting of glassy poly(methyl methacrylate) branches and a rubbery poly(butyl acrylate) backbone were grafted from 100 nm diameter SiNPs by surface-initiated atom transfer radical polymerization. The comb-shaped polymer brush-grafted SiNPs produced self-standing films with a face-centered cubic ordered lattice structure via solvent-casting. The composite films showed rubber elasticity because of the interparticle rubbery polymer brush boundary phase. The ordered lattice exhibited significant alignment and distortion in response to the macroscopic film strain, and then reproduced the initial ordered lattice after unloading.

Self-healing materials are of fundamental interest and practical importance. Herein we report the synthesis of a new class of self-healing materials, formed by the copolymerization of ethylene and anisyl-substituted propylenes using a sterically demanding half-sandwich scandium catalyst. The copolymerization proceeded in a controlled fashion, affording unique multi-block copolymers composed of relatively long alternating ethylene-alt-anisylpropylene sequences and short ethylene–ethylene units. By controlling the molecular weight and varying the anisyl substituents, a series of copolymers that show a wide range of glass-transition temperatures (Tg) and mechanical properties have been obtained. The copolymers with Tg below room temperature showed high elastic modulus, high toughness, and remarkable self-healability, being able to autonomously self-heal upon mechanical damage not only in a dry environment but also in water and aqueous acid and alkaline solutions, while those with Tg around or above room temp...

The ion-specific hydration states of zwitterionic poly(3-( N-2-methacryloyloxyethyl- N, N-dimethyl)ammonatopropanesulfonate) (PMAPS) brushes in various aqueous solutions were investigated by neutron reflectivity (NR) and atomic force microscopy (AFM). The asymmetric hydration state of the PMAPS brushes was verified from the NR scattering-length density profiles, while the variation in their swollen thickness was complementary as determined from AFM topographic images. PMAPS brushes got thicker in any salt solutions, while the extent of swelling and the dimensions of swollen chain structure were dependent on the ion species and salt concentration in the solutions. Anion specificity was clearly observed, whereas cations exhibited weaker modulation in ion-specific hydration states. The anion specificity could be ascribed to ion-specific interactions between the quaternary ammonium cation in sulfobetaine and the anions. The weak cation specificity was attributed to the intrinsically weak cohesive interactions between the weakly hydrated sulfonate anion in sulfobetaine and the strongly hydrated cations. The ion-specific hydration of PMAPS brushes was largely consistent with the ion-specific aggregation state of the PMAPS chains in aqueous solutions.

Polyzwitterions have emerged as a new class of antifouling materials alternating poly(ethylene glycol). The exemplary biopassivation and lubrication behaviors are often attributed to the particular chemical structure of zwitterions, which involve a large dipole moment of the charged groups and a neutral net charge, while the hydration state and dynamics also associate with these characteristics. Polymer brushes composed of surface-tethered polyzwitterion chains produced by surface-initiated controlled radical polymerization have been developed as thin films which exhibit excellent antifouling and lubrication properties. In past decades, numerous studies have been devoted to examining the structure and dynamics of polyzwitterion brush chains in aqueous solutions. This feature article provides an overview of recent studies exploring the hydration state of polyzwitterion brushes with specular neutron reflectivity, highlights some newly published work on the nonuniform equilibrium structure, ion concentration dependence, ion specificity, and the effects of charge spacer length in the zwitterions, and discusses future perspective in this field.

Thermal behavior, molecular aggregation structure, and water repellency for poly{2-[(perfluorooctylethyl)carbamate]ethyl}acrylate (PFAUr-C8) were studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), grazing-incidence wide-angle X-ray diffraction (GI-WAXD), contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The impact of the carbamate linker was verified by comparison with poly[2-(perfluorooctyl)ethyl]acrylate (PFA-C8). PFAUr-C8 exhibited two phase transitions at 357 K and 416 K, whereas PFA-C8 showed a single-phase transition at 347 K. Both PFAUr-C8 and PFA-C8 formed a bilayered hexatic smectic-B phase at room temperature. Although the lamellar structure for the fluoroalkyl (Rf) groups was immediately lost in PFA-C8 after disordering of the lateral translational order, PFAUr-C8 maintained a stacked lamellar structure without lateral translational order. PFAUr-C8 exhibited excellent water repellency at room temperature similar to PFA-C8. The outstanding thermal stability of the lamellar structure in PFAUr-C8 is attributed to the cohesive interaction of the carbamate linkage. Thermal behavior, molecular aggregation structure, and water repellency of a comb-shaped fluoropolymer, poly{2-[(perfluorooctylethyl)carbamate]ethyl}acrylate (PFAUr-C8), were investigated. PFAUr-C8 exhibited polymorphic ordered structures, where the stacked lamellar structure of Rf side chains was maintained without their lateral translational order. The cohesive dipolar interactions in the carbamate linkers would induce the thermal stability of the lamellar structure. PFAUr-C8 exhibits superior water repellency.

While polyelectrolyte brushes have received extensive attention due to their particular surface properties, the ion-specific hydration states remain largely unknown. Here, we report the counteranion-specific hydration states of cationic poly[2-(methacryloyloxy)ethyltrimethylammonium] (PMTA) brushes in salt-free water. The water droplet contact angle on the PMTA brushes depends on the counteranion species, and the order is consistent with the Hofmeister series. Weakly hydrated chaotropic counteranions are strongly bound to weakly hydrated quaternary ammonium (QA+) cations in the PMTA brush chains, which induces a reduction in the ζ-potential, dehydration, and collapse of the PMTA brushes. The PMTA brushes with strongly hydrated chloride counteranions produce a more diffuse tail and less swollen bound layer under salt-free deuterium oxide than brushes with weakly hydrated thiocyanate counteranions. Ion pairing disturbs the ordering of hydrated water in the PMTA brushes. Our work enhances the understanding o...

Random copolymers (P(M100-m/T m )) composed of 2-methacryloyloxyethyl phosphorylcholine (MPC), which suppresses protein adsorption, and 3-(triethoxysilyl)propyl methacrylate (MTEOS), which can be covalently fixed on a glass surface, were prepared via photoinitiated radical polymerization. When P(M100-m/T m ) was coated on a glass surface, a protein antifouling effect could be observed because of the presence of MPC units on the glass surface. To confirm the coating of the glass surface with P(M100-m/T m ) by fluorescence microscopy, pyrene-labeled P(M100-m/T m ) was also prepared. An ethanol solution of P(M100-m/T m ) was spin-coated on the glass, which was exposed to NH3 vapor to promote the reaction of the pendant triethoxysilyl groups in P(M100-m/T m ) with silanol groups on the glass. The coating of the glass with MPC was confirmed by fluorescence microscopy. The protein antifouling effects of the P(M100-m/T m )-coated glass were confirmed using fluorescence-labeled proteins. It is expected that P(M100-m/T m ) can be applied as a surface-coating agent on glass containers for protein formulations. Random copolymers (P(M100-m/T m )) composed of 2-methacryloyloxyethyl phosphorylcholine, which suppresses protein fouling, and 3-(triethoxysilyl)propyl methacrylate, which can react covalently to the glass surface, were prepared via photoinitiated radical polymerization. Coating of the glass with P(M100-m/T m ) was confirmed by red fluorescence from Rhodamine 6G. The protein antifouling properties of the P(M100-m/T m ) coating on glass were confirmed using fluorescence-labeled proteins.

The surface reorganization behavior of a crystalline ABCBA-type copolymer and a non-crystalline ABA-type copolymer including poly(2-methacryloyloxyethyl phosphorylcholine) was investigated. The crystalline domain in the block copolymer suppressed the surface reorganization when exposed to either hydrophilic or hydrophobic condition.

One-dimensional (1-D) polymer nanostructures have attracted much attention due to their unique properties and many potential applications in areas such as sensors, transistors, separation, storage, and photovoltaic cells. This is a review of research activities on 1-D polymer nanostructures fabricated by anodic aluminum oxide (AAO) templates. The preparation methods of polymer nanostructures by AAO templates including polymer melt infiltration, polymer solution infiltration, and chemical synthesis are introduced. According to the molecular structure of polymers, the morphology, and properties of seven types of polymers, amorphous homopolymers, amorphous–amorphous block copolymers, amorphous/amorphous polymer blends, semicrystalline homopolymers, semicrystalline/amorphous polymer blends, semicrystalline-amorphous block copolymers, and semicrystalline–semicrystalline block copolymers in nanopores are demonstrated.

Direct surface modification of polymer fibers and films by surface-initiated polymerization has been investigated. The introduction of initiating sites on polymer materials and their successive polymerization produce surface-tethered polymer chains on the polymer surface. The surface-selective modification controls the surface properties, such as wetting, lubrication and anti-fouling, without sacrificing bulk performance. Among the various procedures for introduction of initiating groups and subsequent polymerization proposed to date, this focused review article highlights our studies on polymer brush grafting to electrospun polymer fibers and polymer films through surface-initiated polymerization. We review studies focusing on grafting polymer chains to five different types of solid polymers: poly(methyl methacrylate)-based copolymers, Br-containing polyolefins, poly(vinylidene fluoride-co-trifluoroethylene), poly(butylene terephthalate), and poly(ether-ether ketone). Direct surface modification of polymer fibers and films by surface-initiated polymerizations has been investigated. The introduction of initiating sites on the polymer materials and successive polymerization produce surface-tethered polymer chains on the polymer surface. The surface-selective modification controls the surface properties such as wetting, lubrication and anti-fouling without sacrificing the bulk performances. Researches on grafting polymer chains to five types of polymers, poly(methyl methacrylate)-based copolymer, Br-containing polyolefins, poly(butylene terephthalate), poly(vinylidene fluoride-co-trifluoroethylene) and poly(ether-ether ketone) are reviewed.

Biocompatible and blood-compatible surface modification is urgently needed for stainless steel (SUS)-based human implant devices to avoid inflammation and biofouling. To this end, the use of polymeric surface modifiers, whose surface properties are specifically tailored, is a promising approach since this approach minimizes the impact on device's mechanical properties. However, adhesion between the device and surface modifier is relatively weak, since van der Waals forces are employed, leading to low device durability. To address this issue, this work functionalized poly(ɛ-caprolactone)-b-[poly(α-chloride-ɛ-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine)]2 (PCL-b-(PCL-Cl-b-PMPC)2) with catechol groups via a nucleophilic substitution, whereby the catechol functionalization was optimized. The resultant surface modifier showed strong adhesion toward SUS surfaces, forming a smooth and uniform hydrophilic polymeric film that reduced SUS fouling (i.e., protein). Notably, no significant changes of adhesion between the SUS and thin films (thin film) were observed after immersion for 45 days in a pH 7.4 phosphate buffer solution. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 38–49

Effect of alkyl chain spacer length between the charged groups (CSL) in zwitterionic poly(sulfobetaine) (PSB) brushes on the hydration state was investigated. PSB brushes with ethyl (PMAES), propyl (PMAPS), or butyl (PMABS) CSL were prepared by surface-initiated atom transfer radical polymerization on silicon wafers. Hydration states of the PSB brushes in aqueous solutions and/or humid vapor were investigated by contact angle measurement, infrared spectroscopy, AFM observation, and neutron reflectivity. The PSB brushes are swollen in humid air and deionized water due to the hydration of the charged groups leading to the reduction of hydrated PSB brushes/water interfacial free energy. The hydrated PSB brushes exhibit clear interface with low interfacial roughness due to networking of the PSB brush chains through association of the SBs. The hydrated PSB brushes produce diffusive swollen layer in the presence of NaCl because of the charge screening followed by SB dissociation by the bound ions. The ionic strength sensitivity in the hydration got more significant with increasing the CSL in SBs because of the augmentation in partial charge by charged group separation.

Molecular aggregation structure and mechanical as well as thermal properties of novel well-defined multiblock copolymers consisting of crystalline syndiotactic polystyrene (sPS) and rubbery hydrogenated polyisoprene (hPIp) were investigated. The morphology and crystalline ordered structure of the multiblock copolymer films prepared by solvent casting from 1,2-dichlorobenzene solution depended on the volume fraction of sPS (VFsPS) and number of blocks. The multiblock copolymer films exhibited ordered morphology with low crystallinity. The crystallinity of the sPS reduced with decreasing the VFsPS. The pentablock copolymer produced more ordered morphology and less crystallinity than the triblock copolymers. The anisotropic orientation and mechanical stability of the δ form sPS crystals in the spherical sPS domains during uniaxial stretching were demonstrated. Tensile testing and dynamic mechanical analysis indicated that these multiblock copolymer films with appropriate sPS fraction are strong, tough, and e...

The effect of molecular mobility of a pre-crystallized phase on the isothermal crystallization in the microphase-separated lamellar morphology of a strongly segregated crystalline-crystalline block copolymer, poly(ethylene glycol)- block -poly(perfluorooctylethyl acrylate) (PEG- b -PFA-C 8 ), was investigated. The diblock copolymer produced a microphase-separated lamellar morphology in the melt state, and the precedent crystallization of PFA-C 8 blocks provided the lamellar confinement field. The counter PEG block crystallized within the lamellar confinement field. The molecular mobility of the pre-crystallized PFA-C 8 phase was modulated by the thermal history. The structural evolution was monitored by a complementary combination of in situ time-resolved simultaneous small-angle X-ray scattering/wide-angle X-ray diffraction measurements and thermal analyses. The degree of crystallinity and the melting temperature of the PEG crystals were associated with the molecular mobility of the pre-crystallized PFA-C 8 phase. The highly packed PFA-C 8 phase (higher-ordered phase) constrained the PEG crystallization, whereas the loosely packed PFA-C 8 phase (lower-ordered phase) caused a weak restriction in the PEG crystallization to give relatively ordered PEG crystals. Subsequent crystallization in a confinement field of crystalline-crystalline block copolymers was controlled by adjusting the molecular mobility of the pre-crystallized phase.

Poly(etheretherketone) (PEEK) substrate surface was modified with charged cationic poly(2-(methacryloyloxy) ethyltrimethylammonium chloride) (PMTAC) and anionic poly(3-sulfopropyl methacrylate potassium salt) (PSPMK) polymer brushes through surface-initiated radical polymerization triggered by UV light exposure of benzophenone groups in PEEK backbone as an initiator. After extensive UV light exposure, the PEEK surface was covered with grafted polyelectrolyte chains and exhibited swollen polyelectrolyte brushes with high roughness under water, indicating high graft density and wide molecular weight distributions of PMTAC and PSPMK brushes. The hydrated polyelectrolyte brushes on PEEK surface induce significant air bubble repellency in water. Thus, thickening of swollen polyelectrolyte brushes dramatically reduces the friction coefficient of PEEK surface under a wet condition.

Water existing in the vicinity of polyelectrolytes exhibits unique structural properties, which demonstrate key roles in chemistry, biology, and geoscience. In this study, X-ray absorption and emission spectroscopy was employed to observe the local hydrogen-bonding structure of water confined in a charged polyelectrolyte brush. Even at room temperature, a majority of the water molecules confined in the polyelectrolyte brush exhibited one type of hydrogen-bonding configuration: a slightly distorted, albeit ordered, configuration. The findings from this study provide new insight in terms of the correlation between the function and local structure of water at the interface of biological materials under physiological conditions.

2-Methacryloyloxyethyl choline phosphate (MCP) was synthesized by a ring-opening reaction of cyclic phosphates with 2-(dimethylaminoethyl methacrylate). The crude MCP consisted of an endo-cyclic de...

A feasible processing of zwitterionic polymer-grafted anodic aluminum oxide (AAO) membranes by surface-initiated atom transfer radical polymerization (SI-ATRP) and the geometric effect on the polymer chain growth in the confined nanopores were investigated. A zwitterionic poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate) (PMAPS) brush was produced on an AAO membrane via introduction of an initiator with a phosphonate group and subsequent SI-ATRP. The PMAPS-grafted AAO membranes were characterized by water droplet contact angle measurement, size exclusion chromatography (SEC), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and laser Raman micro-spectroscopy. The linear relationship between the grafting yield (Y) of the PMAPS brush and number-average molecular weight (Mn) of the unbound PMAPS indicates that there is no significant geometric effect on the chain growth under the spatial confinement inside the nanopores with diameters of ∼200 nm. The PMAPS brushes were diminished near the center section along the nanopores because the monomer supply was retarded. The capability of the PMAPS-grafted AAO membranes for inorganic nanoparticle immobilization was also demonstrated using gold nanoparticles (AuNPs) through ion-exchange and reduction processes.

Polymers composed of polycyclic aromatic planar diimide (PCAD) units and flexible rubbery poly(propylene glycol) (PPG) chains were synthesized, and the morphology and viscoelasticity were investigated. The polymers were synthesized by polycondensation of naphthalene or perylene tetracarboxylic dianhydrides with PPG-diamines and subsequent thermal imidization. The thermal and viscoelastic properties were measured by differential scanning calorimetry and dynamic mechanical analysis, respectively. The molecular aggregation structure was explored by infrared spectroscopy, wide-angle X-ray diffraction and small-angle X-ray scattering measurements. The PCAD units associate in the PPG continuum by the electromagnetic interaction of π electrons on the planar aromatic rings to build a stacked structure. The morphology and viscoelastic characteristics depend on the PCAD structure and molecular weight of the PPG segments, and the polymers composed of perylene diimide units and high molecular weight PPG chains show rubber elasticity because of the well-segregated morphology. The thermal stability was enhanced by PPG chain end capping by thermally stable PCAD units.

The surface dynamics of polyhedral oligomeric silsesquioxane (POSS)-functionalized polystyrene (PS-POSS) thin films above the glass transition temperature were studied by grazing-incidence X-ray photon correlation spectroscopy in order to elucidate the effects of POSS at the end of the polystyrene chains. Much slower fluctuations were observed in the surface of PS-POSS thin films than in the polystyrene thin films, despite the negligible difference in their bulk viscosity. Quantitative analysis based on fluctuation-dissipation theorem indicated that there is a high-viscosity layer at the surface of the PS-POSS films, and that the substrate interface originated from POSS segregation.

Hybrid hydrogels composed of imogolite fibrous nanotube (IG) and hyaluronic acid (HA) were prepared. Hexamethylenediamine (HMDA) was used as a non-toxic chemical cross-linker. The homogeneous dispersion of IG in the HA solution was accomplished by careful pH control, and subsequent chemical cross-linking provided mechanically stable self-standing hybrid hydrogels. The IG/HA hybrid hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), swelling test, compression test, oscillatory rheological analysis, and enzymatic degradation test. The IG/HA hybrid hydrogels show better mechanical properties and lower degradation rate than native HA-based hydrogels without IG hybridization because the cross-linking density increases by incorporation of additional IG network into chemically cross-linked HA network.

The phase behavior of polystyrene (PS) brushes in cyclohexane (CHX) was investigated, for the first time, by environmental atomic force microscopy as a function of the graft density and temperature. The polystyrene brushes of three different graft densities exhibited island-, bicontinuous-, and hole-shape microdomains in the direction parallel to the substrate. The size of such “in-plane” microdomains is close to the end-to-end distance of PS brush chain due to the anchoring of one of the chain ends of PS brushes to the substrate. The microdomain structure disappeared as the temperature increased, and new structure with same morphological features reappeared by lowering temperature. This reversible temperature response corresponds to the in-plane phase separation of the PS brush/CHX system. The UCST type binodal line shifted toward slightly lower temperature in the PS brush/CHX system compared to that of the corresponding nongrafted polymer solution, i.e., PS/CHX system, in excellent agreement with our pr...

The change in the crystal structure of polymer-grafted nanoparticles during uniaxial stretching was investigated by simultaneous ultra-small-angle X-ray scattering and stress–strain measurement., A molded film of single-component polymer-grafted nanoparticles (SPNP), consisting of a spherical silica core and densely grafted polymer chains bearing hydrogen-bonding side groups capable of physical crosslinking, was investigated by in situ ultra-small-angle X-ray scattering (USAXS) measurement during a uniaxial stretching process. Static USAXS revealed that the molded SPNP formed a highly oriented twinned face-centered cubic (f.c.c.) lattice structure with the [11−1] plane aligned nearly parallel to the film surface in the initial state. Structural analysis of in situ USAXS using a model of uniaxial deformation induced by rearrangement of the nanoparticles revealed that the f.c.c. lattice was distorted in the stretching direction in proportion to the macroscopic strain until the strain reached 35%, and subsequently changed into other f.c.c. lattices with different orientations. The lattice distortion and structural transition behavior corresponded well to the elastic and plastic deformation regimes, respectively, observed in the stress–strain curve. The attractive interaction of the hydrogen bond is considered to form only at the top surface of the shell and then plays an effective role in cross-linking between nanoparticles. The rearrangement mechanism of the nanoparticles is well accounted for by a strong repulsive interaction between the densely grafted polymer shells of neighboring particles.

We have prepared the amidinium-carboxylate salt bridge-based supramolecular network polymers from a carboxy-terminated telechelic poly(n-butyl acrylate) and a linear polyamidine having N,N′-di-substituted acetamidine group in the main chain. FTIR measurements indicated that the salt bridge was attributed to the three-dimensional network formation. Virtually, no fluidity was observed for the blend containing equimolar amounts of the carboxyl group and the amidine group, which showed a high G′ value of about 1 MPa at −5 °C. For comparison, the supramolecular network polymers crosslinked by ammonium-carboxylate salt were prepared using a linear polyethyleneimine instead of the polyamidine. The blend with equimolar amounts of the carboxyl group and the secondary amino group showed liquid-like fluidity with a G′ value of about 0.01 MPa at −5 °C, which was attributed to the fact that a certain amount of the carboxyl group remained as its free form, as evidenced by FTIR analysis. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2148–2155

The dynamic covalent exchange reactions of side chains in polymer brushes on nanoparticles were successfully demonstrated, and the dispersibility of the nanoparticles after the exchange reactions was investigated in some solvents. A polymer brush with exchangeable alkoxyamine side chains was prepared by surface-initiated atom transfer radical polymerization on silica nanoparticles. Fluorinated and ionic polymers were grafted to the polymer brush via radical exchange reactions of alkoxyamine moieties. The chemical composition of the polymer brushes on nanoparticles before and after the exchange reactions was investigated by X-ray photoelectron spectroscopy (XPS). The XPS measurements indicated that the side chains of the polymer brushes were converted to the corresponding polymers. In addition, the grafted side chains could be detached from the surface of the nanoparticles through a further radical exchange process by treating with alkoxyamines. The XPS results indicate that the structure of the de-grafted polymer brush is nearly the same as the original, thus demonstrating the reversibility of the reactions. Furthermore, the dispersibility of the nanoparticles in solution could be changed by the reversible grafting reactions. A polymer brush with exchangeable alkoxyamine side chains was prepared by surface-initiated atom transfer radical polymerization on silica nanoparticles. Fluorinated and ionic polymers were grafted to the polymer brush and the grafted side chains could be detached from the surface of the nanoparticles via radical exchange reactions of alkoxyamine moieties. The chemical composition of the polymer brushes on nanoparticles before and after the exchange reactions was investigated by X-ray photoelectron spectroscopy. The dispersibility of the nanoparticles in solution could be changed by the reversible grafting reactions.

Hybrid hydrogels composed of hyaluronic acid (HA) and halloysite nanotubes (HNTs) were prepared via photocrosslinking of HA and HNTs functionalized with vinyl groups. These hybrid hydrogels showed enhanced mechanical properties without sacrificing good swelling capability, which is crucial for biomedical applications.

Natural rubber (NR) films from various mixing ratios of large- (LRP) and small rubber particles (SRP) were prepared through latex and solution casting methods. Film-forming behaviours of the resulting films were investigated by monitoring their surface characteristics using atomic force microscopy (AFM). When the SRP portion was higher, the surface of the latex-cast films was found to be smoother as smaller particles protruded out of the surface less than larger ones did. AFM phase micrographs revealed a hexagonal shape of packed rubber particles (RPs) of the LRP film, while the RPs in the other samples were sphere-like. After aging under ambient conditions, the packed RPs were flattened while retaining their RP boundaries, creating a supporting framework within the rubber matrix. On the contrary, when the rubber film was cast from a toluene solution, the characteristic of RP boundaries disappeared and became aggregates of the membrane components on the film surface. The latex-cast films performed much better in mechanical strength than the solution-cast films did due to the destruction of the supporting framework arisen from the non-rubber components at the RP boundaries of the solution-cast film. An inhomogeneous density distribution produced by the non-rubber aggregates in the latex-cast films was observed in small angle X-ray scattering measurements.

Nature-inspired material design concepts and recent progress on anti-fouling polymer materials are reviewed, and our recent researches on anti-fouling studies with polymer brushes are summarized. Zwitterionic polyelectrolyte brush immobilized surfaces represent significant anti-fouling for bio-macromolecules, oil foulants, marine fouling organisms and pipeline foulants. The anti-fouling mechanism was considered on the basis of the wetting, lubrication, hydrated chain dimension and hydrogen-bonding structure of hydrated water in the polyelectrolyte brushes.

Repeated mechanical scission and recombination of dynamic covalent bonds incorporated in segmented polyurethane elastomers are demonstrated by utilizing a diarylbibenzofuranone-based mechanophore and by the design of the segmented polymer structures. The repeated mechanochemical reactions can accompany clear colouration and simultaneous fading.

A solvent free oxidative coupling reaction of 3-hexylthiophene (3HT) within a nanocavity is reported. It is found that 3HT can be encapsulated in nanocavities larger than 1 nm, which corresponds to the size of the molecule. In this case, the side reaction at the 4-position in 3HT is regulated.

The anti-fouling character of polymer brushes against marine organisms was investigated by performing settlement tests with barnacle cypris larvae and mussel larvae in their adhesion period, as well as a marine bacteria colonization test. The surface charge and hydration state in saline seawater appear to be important factors in the versatile anti-fouling performance of zwitterionic polyelectrolyte brushes.

Topologically ordered surfaces with a polymer brush-grafted layer were prepared by a combination of nano-imprinting (NI) and surface-initiated atom transfer radical polymerization (SI-ATRP). The molecular aggregation state and the wetting were evaluated by synchrotron radiation X-ray analyses and water droplet contact angle measurements, respectively. An ordered topography was fabricated onto a spin coated thin film of a polymethacrylate-based copolymer with polymerization initiating sites [P(MMA-co-BIEM)] by NI. Then poly{2-(perfluorooctyl)ethyl acrylate} (PFA-C8) chains were grafted onto the thin film by SI-ATRP. The surface geometry was maintained after PFA-C8 grafting when the thickness of the grafted polymer layer was sufficiently thin to a scale of the concave region. The modified P(MMA-co-BIEM) thin film surface was water repellent by a synergetic effect of the surface geometry and the low surface free energy of the grafted PFA-C8 layer.

Autonomously substitutable organosilane thin films based on diarylbibenzofuranone (DABBF) units were prepared, and the radical exchange reactions of the DABBF units at the surface resulted in chemi...

This chapter reviews the anti-(bio)fouling systems based on polymer brushes. Charged polymer brushes are well-hydrated in aqueous solutions to produce liquid-infused smooth interface. Because of the extremely low interfacial tension in the water-infusion soft interfaces and water, the hydrated charged polymer brushes exhibit outstanding anti-fouling capability in aqueous solutions. We present here anti-(bio)fouling properties of the charged polymer brushes to oils, asphaltenes, and marine fouling organisms including barnacle cypris larvae, mussel larvae, and marine bacteria.

The synergistic interactions between the α-amine and the carboxylic acid in an amino acid have recently been studied as bio-based zwitterions. Here, we report a new amphiphilic polymer containing glutamic acid grafted to the end of a dodecyl polymer side chain, which contains the α-amine and the γ-carboxylic acid of the glutamic acid moiety. The polymer self-assembled into a multilayered structure in the thin film, and the glutamic acid moieties in the polymer side chains were exposed to the polymer film/water interface. Annealing the sample enhanced the formation of a well-oriented lamellar structure in the films. Due to the presence of the glutamic acid moieties at the interface, the surface charge was controllable by pH in buffer solutions, resulting in zwitterionic character at neutral pH. It has been widely accepted that zwitterionic surfaces can exhibit non-fouling for proteins. Interestingly enough, the polymer film showed charge-selective protein adsorption since the synergistic interaction between the α-amine and the γ-carboxylic acid was weaker than conventional amino acid-based zwitterionic systems. This is due to the separated state of the functional groups by a three carbon spacer.

The chain stiffness and local chain conformation of atactic poly(α-methylene-γ-butyrolactone) (PMBL), which is a side chain cyclic structural analog of poly(methyl methacrylate) (PMMA), with a weight-average molecular weight (Mw) ranging from 2.8 × 103 to 2.6 × 106 in N,N-dimethylformamide (DMF) and γ-butyrolactone (GBL) were characterized by size exclusion chromatography with a multi-angle light-scattering detector (SEC-MALS) and synchrotron radiation small-angle X-ray scattering (SAXS). Based on the Kratky-Porod worm-like chain model, the scattering functions and the Mw dependence of z-average root-mean-square radius of gyration z1/2 yielded the Kuhn segment lengths λ−1, the diameter of the PMBL chains d, and the excluded-volume strengths in DMF and GBL. The local conformation of atactic PMBL in DMF and GBL were slightly larger than those of atactic PMMA, due to the presence of the conformationally rigid lactone ring structure.

The adsorption behavior of a model compound for surface-active component of asphaltenes, N-(1-hexylheptyl)-N′-(12-carboxylicdodecyl) perylene-3,4,9,10-tetracarboxylic bisimide (C5Pe), and detachment behavior of asphaltene deposit films for high-density polymer brushes were investigated. Zwitterionic poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate (PMAPS) brushes and hydrophobic poly(n-hexyl methacrylate) (PHMA) brushes exhibit less C5Pe adsorption than poly(methyl methacrylate) (PMMA). The asphaltene deposit films on the PHMA brush detached in a model oil (toluene/n-heptane = 1/4 (v/v)), and the asphaltene films on the PMAPS brush detached in water. The antifouling character was explained by the interface free energy for the polymer-brush/asphaltenes (γSA) and polymer-brush/toluene (γSO).

The effect of α-substituent on the molecular motion and wetting behavior of poly{2-(perfluorobutyl)ethyl acrylate} [PFA-C4], poly{2-(perfluorobutyl)ethyl methacrylate} [PFMA-C4], poly{2-(perfluorobutyl)ethyl α-fluoroacrylate} [PFFA-C4], and poly{2-(perfluorobutyl)ethyl α-chloroacrylate} [PFClA-C4] films were characterized by dynamic contact angle measurement, lateral force microscopy (LFM), wide angle X-ray diffraction (WAXD), and X-ray photoelectron spectroscopy (XPS). WAXD of oriented PFClA-C4 fiber suggested the presence of rod-like chain due to the presence of bulky α-substituent. The glass transition temperature (Tg) of PFFA-C4 and PFClA-C4 were well above the room temperature. The water repellencies of PFFA-C4 and PFClA-C4 were as high as that of PFMA-C4 and their oil repellency of PFFA-C4 and PFClA-C4 was higher than the PFMA-C4. This result was originated from the low main chain mobility of PFFA-C4 and PFClA-C4 due to the presence of bulky α-substituents. The effect of molecular motion on water repellency was clarified by the results of temperature dependence studies of dynamic contact angle, LFM, and surface chemical composition measured by XPS.

Double ring-banded spherulites of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV with 12 wt% 3HV) blending with 30 wt% amorphous poly(vinyl acetate) (PVAc) were examined using polarized light optical microscopy (POM), scanning electron microscopy (SEM), atomic-force microscopy (AFM) and micro-beam X-ray diffraction. A ring-banded spherulite of PHBV/PVAc 70/30 blend was linearly scanned across the bands in 5 μm steps by means of micro-beam X-ray diffraction. Solvent-etching and fracturing were utilized for probing the interior lamellar textures of the blend samples. Detail interior lamellar orientations in bulk film of PHBV three-dimensional ring-banded spherulites were revealed. SEM and micro-beam X-ray diffraction results suggest that the PHBV lamellar orientation gradually change along the radial growth direction with right-handed rotation sense. The blending effect in band pattern (width and regularity) of PHBV/PVAc blend was discussed.

The effectiveness of energy-resolved (ER) X-ray photoelectron spectroscopy (XPS) with synchrotron radiation (SR) soft X-ray source for analysis of the outermost chemical composition of polymer materials is demonstrated. The surface molecular aggregation state of poly(ethylene glycol) (PEG)/poly(perfluorooctylethyl acrylate) (PFA-C8) was confirmed using ER-XPS. The XPS with SR soft X-ray source detect only the single bilayer structure of the PFA-C8 component, whereas the XPS with Mg Kα X-ray source detect both the PFA-C8 component at the outermost surface and PEG component at the interior.

Reversible hydrophilicity control of a radically exchangeable polymer brush with dynamic covalent linkages was successfully demonstrated. A polymer brush with alkoxyamine units was prepared via surface-initiated atom transfer radical polymerization, and reversible surface hydrophilicity control was achieved via dynamic covalent exchange reactions of alkoxyamines. Exchange reactions between alkoxyamine units in the side chains of the polymer brush and the terminal of poly(4-vinylpyridine) (P4VP) were carried out in order to prepare a side-chain functionalized polymer brush. Subsequent quaternization of P4VP chains with iodomethane was carried out to prepare a more hydrophilic surface. In addition, a de-grafting reaction of the quaternized P4VP side chains was performed to confirm reversibility of the alkoxyamine via radical exchange reactions on the surface. All the composition and wettability changes were investigated via X-ray photoelectron spectroscopy and contact angle measurements.

Reversible cross-linking reactions of alkoxyamine-appended polymers with low glass transition temperature ( T g ) were successfully carried out under bulk conditions. The low- T g polymers with alkoxyamine units in the side chains were synthesised by radical copolymerisation of 2-ethylhexyl acrylate and two kinds of alkoxyamine-containing acrylate monomers. By heating the low- T g polymers under bulk conditions at 100 °C, cross-linked polymers were formed by radical exchange reactions between alkoxyamine units, and a transition from a liquid-like flowable polymer state to a rubber-like polymer state was confirmed. A de-cross-linking reaction was also accomplished by radical exchange reactions between the cross-linked polymers and an added alkoxyamine-containing small molecule or stable nitroxyl radical, which resulted in transition to the flowable state again. The structural transition between low- T g linear polymers and cross-linked polymers were characterised by 1 H and 13 C NMR spectroscopy, Fourier transform infrared spectroscopy, rheology measurement, swelling experiment, and gel permeation chromatography measurement.

Liquid repellency of comb-shaped polyacrylates with perfluoroalkyl side-chains associates with the ordered structure of the side-chains at the surface. The molecular aggregation structure and surface properties of poly{2-[(perfluorohexylethyl)carbamate]ethyl}acrylate (PFAUr-C6) were studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM), powder wide-angle X-ray diffraction (WAXD), grazing incidence wide-angle X-ray diffraction (GI-WAXD), temperature-controlled Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and X-ray photoelectron spectroscopy (XPS). Poly[2-(perfluorohexyl)ethyl]acrylate (PFA-C6) was compared with PFAUr-C6 to verify the effect of carbamate linkage on the aggregation structure and surface properties. The perfluorohexyl groups in PFAUr-C6 produced a double-layered smectic structure, whereas the perfluorohexyl groups in PFA-C6 showed no ordered structure. The double-layered smectic structure in PFAUr-C6 was induced by the hydrogen bonding interaction in the carbamate linkers. PFAUr-C6 showed poor water repellency similar to PFA-C6 because of the rapid surface rearrangement. Although the perfluorohexyl groups produced smectic order structure at the film surface, the lack of positional order in the smectic layers and the low ordered structure content allowed the surface rearrangement.