Optical properties of colloidal crystalline arrays composed of hollow polystyrene spheres

We have evaluated the optical properties of close‐packed and non close‐packed colloidal crystalline arrays made of hollow polystyrene spheres. Close‐packed colloidal crystalline arrays were fabricated by simple evaporation of dispersions, whereas nonclose‐packed colloidal crystalline arrays were fabricated by exploiting electrostatic interactions between the spheres in aqueous dispersion. Optical properties of the arrays were estimated from angle‐resolved reflection spectra. The Bragg diffraction peak of the colloidal crystalline array made of hollow spheres was of shorter wavelength than in the case of solid spheres, not only for the close‐packed array but also for the nonclose‐packed array. These shifts were caused by a decrease in the effective refractive index n_eff with decreasing particle refractive index. We have found that this relationship could be explained by the simple equation n_eff = n_particle?+ n_solvent (1 ? ?), where ? is the volume fraction of the particles, for both close‐packed and non close‐packed arrays. The current work suggests new possibilities for the creation of advanced colloidal crystals. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2364–2368, 2007     

New method for fabricating an α‐fetoprotein affinity monolithic polymer array

Bisphenol A based epoxy acrylate (BABEA), a commercial UV‐curable material, was introduced as a crosslinker for the fabrication of an epoxy‐functionalized monolithic polymer array through UV‐initiated copolymerization with glycidyl methacrylate as the functional monomer and poly(ethylene glycol) 200 as the porogen. Scanning electron microscopy images showed that the monolithic poly(bisphenol A based epoxy acrylate‐co‐glycidyl methacrylate) [poly(BABEA‐co‐GMA)] exhibited a well‐controlled skeletal and well‐distributed porous structure. The α‐fetoprotein (AFP) immunoaffinity monolithic polymer array prepared by the immobilization of AFP on epoxy‐functionalized monolithic arrays was used as an immunosensor for chemiluminescent AFP detection. X‐ray photoelectron spectroscopy results indicate that the AFP antibody was successfully immobilized on the monolithic poly(BABEA‐co‐GMA) array. With a noncompetitive immune‐response format, the proposed AFP immunoaffinity array was demonstrated as a low‐cost, flexible, homogeneous, and stable array for AFP detection. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41792.     

Deposition of Nanostructured Fluorine‐Doped Hydroxyapatite Coating from Aqueous Dispersion by Suspension Plasma Spray

In this study, we prepared an aqueous dispersion of fluorine‐doped hydroxyapatite (FHA) nanoparticles by a wet chemical method. For the first time, the as‐prepared aqueous dispersion of FHA nanoparticles was directly used as suspension for depositing nanostructured FHA coating on stainless steel substrate by suspension plasma spray (SPS) method. Field‐emission scanning electron microscopy images confirm that the coating was nanostructured. X‐ray Diffraction pattern, Fourier‐transform infrared spectroscopy, and Raman spectra show that the as‐sprayed coating was FHA phases. The experimental result confirmed that OH^? and F^? ions have been well kept in FHA crystal lattice and structural integrity has been maintained during SPS process by using an aqueous dispersion of FHA nanoparticles. The potentiodynamic polarization and electrochemical impedance spectroscopy results prove that the nanostructured FHA coating can greatly enhance the anticorrosion performance of stainless steel in phosphate‐buffered saline solution.     

Studies on CoSalen immobilized onto N‐(4‐methylimidazole)‐chitosan

A chitosan (CS) derivative, N‐(4‐methylimidazole)‐chitosan (MIC), was synthesized, and a cobalt (II) complex of bis(salicylideneethylene diamine), (CoSalen), was immobilized on it. The structure of the polymer‐immobilized CoSalen was characterized by elemental analysis, IR, XPS, fluorescence and ESR spectroscopy. It was demonstrated that the immobilization of CoSalen was realized through the coordination of a nitrogen atom of the pendant group, imidazole in MIC, to the Co(II) in CoSalen. The immobilized polymer complex is more efficient than the corresponding monomeric complex in catalyzing the oxidation of DOPA using oxygen. The results may be attributed to a site isolation effect offered by the supporting polymer chain. A mechanism similar to that for enzymatic catalysis was proposed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2431–2436, 2006     

Effects of solvents on the morphology and conductivity of poly(3,4‐ethylenedioxythiophene):Poly(styrenesulfonate) nanofibers

In this study, the effect of solvents on the morphology and conductivity of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) nanofibers is investigated. Conductive PEDOT:PSS nanofibers are electrospun by dissolving a fiber‐forming polymer, polyvinyl alcohol, in an aqueous dispersion of PEDOT:PSS. The conductivity of PEDOT:PSS nanofibers is enhanced 15‐fold by addition of DMSO and almost 30‐fold by addition of ethylene glycol to the spinning dopes. This improvement is attributed to the change in the conformation of the PEDOT chains from the coiled benzoid to the extended coil quinoid structure as confirmed by Raman spectroscopy, X‐ray diffraction, and differential scanning calorimetry. Scanning electron microscopy images show that less beady and more uniform fiber morphology could be obtained by incorporation of ethylene glycol in the spinning dopes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40305.     

Ultrasound‐assisted coating of nylon 6,6 with silver nanoparticles and its antibacterial activity

A silver/nylon 6,6 nanocomposite containing 1 wt % metallic silver has been produced from an aqueous solution of silver nitrate in the presence of ammonia and ethylene glycol by an ultrasound‐assisted reduction method. The structure and properties of nylon 6,6 coated with silver have been characterized with X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, energy‐dispersive X‐ray, X‐ray photoelectron spectroscopy, Raman spectroscopy, and diffused reflection spectroscopy measurements. The nanocrystals of pure silver, 50–100 nm in size, are finely dispersed on the polymer surface without damaging the nylon 6,6 structure. This silver–nylon nanocomposite is stable to many washing cycles and thus can be used as a master batch for the production of nylon yarn by melting and spinning processes. The fabric knitted from this yarn has shown excellent antimicrobial properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1423–1430, 2007     

Mechano‐Morphological Characterization of Polyethylene‐Glycol Based Polyurethane Microgel

Segmental polyurethanes (PU) with hydrophilic segments form colloidal dispersions which are ultimately arrested into gel‐like structure in aqueous continuous phase owing to the differential interactions between polymer and solvent. These structural states of amphiphilic PUs evolve hierarchically, but the structure‐function correlation between PU colloidal dispersion and gels is not clear. Here, this correlation is defined from the mechanomorphology of hydrophilic polyethylene glycol based PU which forms dispersions and finally transforms into gel‐structure. Morphological and rheological analyses show that PU with comparable hydrophilic and hydrophobic content forms attractive colloids with self‐similar fractal microstructures whereas PU with increased hydrophilic character forms space‐filling colloids without any defined organization. Furthermore, colloidal dispersions are densified under shear or gravity to form gel where gel mechanics is defined by colloidal particle organization and the morphology is dependent on gelation mode. This stepwise organization of PU colloidal particles into microgel can independently control microgel mechanics and morphology.

     

Synthesis and characterization of amine‐functionalized amphiphilic block copolymers based on poly(ethylene glycol) and poly(caprolactone)

A series of amine‐functionalized block copolymers, poly(caprolactone)‐block‐poly(ethylene glycol) (PCL‐b‐PEG), were synthesized by ring‐opening bulk polymerization (ROP) of ε‐caprolactone (ε‐CL) initiated through the hydroxyl end of the amino poly(ethylene glycol) (PEG) used as a macroinitiator in the presence of stannous 2‐ethylhexonoate [Sn(Oct)₂]. The polymerization and end functionality of the polymer were studied by different physicochemical techniques (¹H NMR, Fourier transform infrared and X‐ray photoelectron spectroscopy, gel permeation chromatography and thermogravimetric analysis). Thermal, crystalline and mechanical properties of the polymer were thoroughly analyzed using differential scanning calorimetry, wide‐angle X‐ray diffractometry and tensile testing, respectively. The results showed a linear improvement in crystallinity and mechanical properties of the polymer with the content of PEG. Thus the synthesized functional polymers can be used as excellent biomaterials for the delivery of polyanions, as well as macroinitiators for the synthesis of A–B–C‐type block copolymers. Copyright © 2006 Society of Chemical Industry     

Study of the effect of organic clay on the shear‐induced crystallization of high‐density polyethylene through dynamic‐packing injection molding

Organic nanoparticles as heterogeneous nucleators have a great effect on the crystallization of polymer matrices in nanocomposite systems, and the effect will be enhanced under shear flow. A home‐made dynamic‐packing injection molding (DPIM) device was developed to explore the effect of organic clay on the shear‐induced crystallization of high‐density polyethylene (HDPE). Differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD) and scanning electron microscopy (SEM) were used to characterize the flow‐induced crystalline structure of HDPE/clay nanocomposite injection moldings. It was found that higher crystallinity and thicker crystal planes which contribute to the improvement of mechanical properties were achieved in HDPE/clay nanocomposite samples prepared by DPIM. DSC results clearly showed that an increase of about 16% in crystallinity was achieved in dynamic HDPE/clay nanocomposite samples compared with traditional unfilled HDPE samples. WAXD confirmed that dynamic HDPE/clay nanocomposite samples had maximum crystal sizes at the (110) and (200) planes of 335 and 305 Å, respectively. SEM images indicated that the arrangement of crystalline structures in dynamic HDPE/clay samples was altered slightly compared with unfilled HDPE samples prepared using the same processing parameters. The results showed that organic clay was beneficial for increasing crystallinity and crystal size in the HDPE/clay nanocomposite system under shear flow. Meanwhile the arrangement of crystalline structures was insignificantly affected by the organic clay, and the preferred regular arrangement of lamellae could still be formed in the dynamic HDPE/clay nanocomposite system. Copyright © 2010 Society of Chemical Industry     

Side‐chain liquid‐crystalline polymers with a limonene‐co‐methyl methacrylate main chain: Synthesis and characterization of polymers with phenyl benzoate mesogenic groups

A new series of liquid‐crystalline polymers with a polymer backbone of limonene‐co‐methyl methacrylate were synthesized and characterized, and the spacer length was taken to be nine methylene units. The chemical structures of the obtained olefinic compound and polymers were confirmed with elemental analysis and proton nuclear magnetic resonance spectroscopy. The thermal behavior and liquid crystallinity of the polymers were characterized with differential scanning calorimetry and polarized optical microscopy. The polymers exhibited thermotropic liquid‐crystalline behavior and displayed a glass‐transition temperature at 48°C. The appearance of the characteristic schlieren texture confirmed the presence of a nematic phase, which was observed under polarized optical microscopy. These liquid‐crystalline polymers exhibited optical activity. A comparison was also made with polyacrylates and polymethacrylate‐based materials. This revealed that the nature of the polymer backbone had a major effect on the liquid‐crystalline properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4595–4600, 2006     

Less‐ordered lamellar structure of intercalated poly(L‐lactide)/organo‐modified montmorillonite hybrids

Hybrids of poly(L ‐lactide)/organophilic clay (PLACHs) have been prepared via a melt‐compounding process using poly(L ‐lactide) (PLLA) and different contents of surface‐treated montmorillonite modified with dimethyl dioctadecyl ammonium‐salt. The crystalline structures of PLLA and dispersion states of clay particles in those PLACHs were investigated by use of wide‐angle X‐ray diffraction, small‐angle X‐ray scattering, transmission electron microscopy (both cross section and replication modes), and polarized optical microscopy. Those structures are viewed from the conformational changes of PLLA chains in the space of a few nanometer widths between silicate galleries to crystalline lamellae of several nanometer thicknesses, and spherulitic textures more than micrometer sizes. After annealing treatments at 115°C for 1 hr, the PLACHs formed coarse‐grained spherulitic textures with 40 μm diameter composed of less‐ordered and fragmented lamellae, caused by the reduced mobility of the PLLA chain due to the dispersed clay particles in the PLLA matrix and the intercalation of the PLLA chains in the silicate galleries. The formation of the interfibril structure accompanied by the fragmented lamellae among the dispersed clay particles was examined. POLYM. ENG. SCI., 46:703–711, 2006. © 2006 Society of Plastics Engineers     

Crystallization behavior of biodegradable amphiphilic poly(ethylene glycol)‐poly(L‐lactide) block copolymers

Poly(ethylene glycol)‐poly(L ‐lactide) diblock and triblock copolymers were prepared by ring‐opening polymerization of L ‐lactide with poly(ethylene glycol) methyl ether or with poly(ethylene glycol) in the presence of stannous octoate. Molecular weight, thermal properties, and crystalline structure of block copolymers were analyzed by ¹H‐NMR, FTIR, GPC, DSC, and wide‐angle X‐ray diffraction (WAXD). The composition of the block copolymer was found to be comparable to those of the reactants. Each block of the PEG–PLLA copolymer was phase separated at room temperature, as determined by DSC and WAXD. For the asymmetric block copolymers, the crystallization of one block influenced much the crystalline structure of the other block that was chemically connected to it. Time‐resolved WAXD analyses also showed the crystallization of the PLLA block became retarded due to the presence of the PEG block. According to the biodegradability test using the activated sludge, PEG–PLLA block copolymer degraded much faster than PLLA homopolymers of the same molecular weight. © 1999 John Wiley amp; Sons, Inc. J Appl Polym Sci 72: 341–348, 1999     

Processing and properties of nano‐ and macro‐hydroxyapatite/poly(ethylene‐co‐acrylic acid) composites

Hydroxyapatite (HAp)/poly(ethylene‐co‐acrylic acid) composites have been synthesized by a solution‐based method, using nanosized (n‐HAp) and coarse hydroxyapatite (c‐HAp) particles, respectively. X‐ray diffraction study has indicated the development of compressive and tensile stresses in composites because of the thermal expansion mismatch between the particles and polymer matrix. Fourier transform infrared absorption spectra and thermal analysis have showed the presence of strong interfacial bonding between the particles and polymer. The surface roughness and the homogeneous dispersion of HAp particles in the polymer matrix have been observed by scanning electron microscopy. A comparison in mechanical properties between composites prepared with n‐HAp and c‐HAp particles, respectively, has been studied. Nanosized particles contribute excellent improvement of mechanical properties of the composites rather than the coarse particles. The uniform dispersion of HAp particles, followed by the improvement in mechanical properties of the composite, provides a means of preparing HAp/polymer composites for low load‐bearing implant applications. POLYM. COMPOS., 27:633–641, 2006. © 2006 Society of Plastics Engineers     

Poly(ethylene glycol)‐Supported Chiral Imidazolidin‐4‐one: An Efficient Organic Catalyst for the Enantioselective Diels–Alder Cycloaddition

A tyrosine‐derived imidazolidin‐4‐one was immobilized on a modified poly(ethylene glycol) and converted in situ into a soluble polymer‐supported catalyst for the enantioselective Diels–Alder cycloaddition of acrolein to 1,3‐cyclohexadiene (up to 92% ee) and 2,3‐dimethyl‐1,3‐butadiene (73% ee). Catalyst recycling (up to four cycles) was accompanied by some loss of the chemical efficiency and marginal erosion of the enantioselectivity.     

Synthesis and surface properties of polystyrene‐graft‐poly(ethylene glycol) copolymers

Polystyrene‐graft‐poly(ethylene glycol) copolymers (PS‐g‐PEG) were successfully synthesized using the “grafting‐through” method. The graft copolymers and the surface properties of their coats were characterized by 1 H‐NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), static contact angle measurement, and atomic force microscopy (AFM). Both DSC and TEM indicated that the graft copolymers had a microphase separated structure. AFM showed the microphase separated structure also occurred at the coat surface, especially at high PEG content, which could also be indirectly confirmed by the XPS and contact angle results. The formation mechanism of the microphase separated structure was discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1458–1465, 2007     

Thermal and surface characterization of polyurethane–urea clay nanocomposite coatings

This paper reports synthesis and characterization of polyurethane–urea (PU‐urea) and the nanocomposites derived from the PU‐urea with silicate clays. Organophilic montmorillonite cotreated by cetyl trimethyl ammonium bromide (CTAB) was synthesized and used to prepare PU‐urea/montmorillonite nanocomposites coatings. PU‐ureas were prepared from polyethylene glycol (PEG), polypropylene glycol (PPG), trimethylol propane (TMP), and 4,4′‐diphenylmethane diisocyanate (MDI) by reacting excess diisocyanate with polyether glycols. The excess isocyanate of the prepolymers was cured with atmospheric moisture. The synthesized moisture cured PU‐urea and nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetric (DSC), and angle resolved X‐ray photoelectron spectroscopy (AR‐XPS). The thermal stability of the PU‐urea nanocomposites was higher relative to the mother PU‐urea films. DSC results showed a slight enhancement in the soft segment glass transition temperature after 3 wt % clay loading. The surface properties showed an enrichment of the soft segment toward the surface. An enhancement in the hard segment composition in the nanocomposite coatings has resulted in enhancing the phase mixing process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2393–2401, 2006     

Infrared spectra and ferro‐electricity of ultra‐thin films of vinylidene fluoride and trifluoroethylene copolymer

The structures of ultra‐thin films of vinylidene fluoride and trifluoroethylene copolymer were characterized using Fourier transform infrared reflection absorption spectroscopy (FTIR‐RAS), FTIR transmission spectroscopy (FTIR‐TRS), atomic force microscopy, and wide‐angle X‐ray diffraction. The ferro‐electricity was determined from polarization charge (a displacement (D)–electric field (E) hysteresis). FTIR‐RAS and FTIR‐TRS measurements showed that the molecular chains of polymers (crystal c‐axis) near the substrate tended to align parallel to the substrate. However, thermal annealing of the sample films at temperatures above 145 °C caused a marked change in molecular alignment of the polymer chains (crystal c‐axis) from parallel to normal to the substrate, and, further, caused a conformation change from trans to partially gauche forms. Copyright © 2007 Society of Chemical Industry     

Miscibility and crystallization behavior of biodegradable poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/phenolic blends

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)/phenolic blends are new miscible crystalline/amorphous polymer blends prepared via solution casting method in this work, as evidenced by the single composition dependent glass transition temperature. The measured T_gs can be well fitted by the Kwei equation with a q value of 13.6 for the PHBV/phenolic blends, indicating that the interaction between the two components is strong. The negative polymer–polymer interaction parameter, obtained from the melting depression of PHBV using the Nishi‐Wang equation, indicating the thermal miscibility of PHBV and phenolic. The spherulitic morphology and crystal structure of PHBV/phenolic blends were studied with polar optical microscopy and wide angle X‐ray diffraction compared with those of neat PHBV. It is found that the growth rates of PHBV in the blends are lower than that in neat PHBV at a given crystallization temperature, and the crystal structure of PHBV is not modified by the presence of phenolic in the PHBV/phenolic blends, but the crystallinity decrease with the increasing of phenolic. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Surface modification of ultra‐high‐molecular‐weight polyethylene. I. Characterization and sintering studies

We performed surface modification of ultra‐high‐molecular‐weight polyethylene (UHMWPE) through chromic acid etching with the aim of improving the performance of UHMWPE's composites with poly(ethylene terephthalate) fibers. In part I of this study, we evaluated the effects of chemical modification on the surface properties of UHMWPE with X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and contact angle measurements. The thermal properties, rheology, and sintering behavior of the modified UHMWPE were compared to those of the base material. XPS and FTIR analysis confirmed the presence of carboxyl and hydroxyl groups on the surface of the modified powders. The substitution of polar groups into the backbone of the polymer decreased its contact angles with water and hexadecane and increased its surface energy, as evidenced by contact angle measurements. The modified UHMWPE was more crystalline than the base resin and less prone to thermal degradation. Although the rheological properties were virtually identical, the modified powders sintered more readily, presumably due to their higher surface energy, which suggested enhanced processability by compression molding. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Comb‐like polymer with sulfo groups and its dispersion and rheological properties in aqueous ceramic suspensions

Two types of new comb‐like polymers were formed as dispersants for aqueous ceramic suspensions with isoprenyloxy poly(ethylene glycol ether), acrylic acid, maleic anhydride as the main starting materials. During the synthesis, one comb‐like polymer introduced sodium methylallyl sulfonate (SMAS) into the reaction media, whereas the other did not. The chemical structure and molecular weight were characterized by Fourier transform infrared spectroscopy and gel permeation chromatography. The effects of the polymers on the dispersion, ζ potential and rheological properties of the kaolin suspensions are discussed in detail. The results indicate that SMAS facilitated chain transfer, controlled the effective charge density of the surface, and increased the electrostatic repulsion force. The kaolin suspensions displayed shear‐thinning behavior on the basis of the electrostatic and steric effects of the comb‐like polymers. The apparent viscosity decreased from 1088 to 258 mPa s with the assistance of the SMAS‐prepared comb‐like polymer as a dispersant. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44563.