Acrylic polymer/silica organic–inorganic hybrid emulsions for coating materials: Role of the silane coupling agent

Acrylic polymer/silica organic–inorganic hybrid emulsions were synthesized by a simple method, that is, a conventional emulsion polymerization and subsequent sol–gel process, to provide water‐based coating materials. The acrylic polymer emulsions contained a silane coupling agent monomer, such as methacryloxypropyltriethoxysilane, to form highly solvent‐resistant hybrid films. On the other hand, the hybrid films from the surface‐modified polymer emulsions, in which the silane coupling agent was located only on the surface of the polymer particles and the particle core was not crosslinked, did not exhibit high solvent resistance. A honeycomblike array structure, which was derived from the polymer particles (diameter ≈ 50 nm) and the silica domain, on the hybrid film surfaces was observed by atomic force microscopy. The crosslinked core part and silane coupling agent containing the shell part of the polymer particles played important roles in attaining high solvent resistance. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4736–4742, 2006     

Influence of multiwall carbon nanotubes on morphological and structural changes during UV irradiation of syndiotactic polypropylene films

The effect of UV irradiation on the morphology and structure of syndiotactic polypropylene (sPP) is investigated both for pure films and those filled with multiwall carbon nanotubes (MWCNTs). UV treatment causes a structural reorganization of pure sPP films. It seems that the incorporation of MWCNTs has a strong stabilizing effect, with nanotubes acting as a limiter of the UV‐induced chain breakage, especially when a good dispersion of carbon nanotubes in the polymer is achieved. The incorporation of MWCNTs introduces a high concentration of defects in the crystal structure of sPP, which limits the UV‐induced growth of crystallites, and prevents the development and propagation of cracks caused by UV irradiation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Functionalization and patterning of reactive polymer brushes based on surface reversible addition and fragmentation chain transfer polymerization

We present the synthesis of reactive polymer brushes prepared by surface reversible addition–fragmentation chain transfer polymerization of pentafluorophenyl acrylate. The reactive ester moieties can be used to functionalize the polymer brush film with virtually any functionality by simple post‐polymerization modification with amines. Dithiobenzoic acid benzyl‐(4‐ethyltrimethoxylsilyl) ester was used as the surface chain transfer agent (S‐CTA) and the anchoring group onto the silicon substrates. Reactive polymer brushes with adjustable molecular weight, high grafting density, and conformal coverage through the grafting‐from approach were obtained. Subsequently, the reactive polymer brushes were converted with amino‐spiropyrans resulting in reversible light‐responsive polymer brush films. The wetting behavior could be altered by irradiation with ultraviolet (UV) or visible light. Furthermore, a patterned surface of polymer brushes was obtained using a lithography technique. UV irradiation of the S‐CTA‐modified substrates leads to a selective degradation of S‐CTA in the exposed areas and gives patterned activated polymer brushes after a subsequent RAFT polymerization step. Conversion of the patterned polymer brushes with 5‐((2‐aminoethyl)amino)naphthalene‐1‐sulfonic acid resulted in patterned fluorescent polymer brush films. The utilization of reactive polymer brushes offers an easy approach in the fabrication of highly functional brushes, even for functionalities whose introduction is limited by other strategies. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Obtaining of hybrid nanocomposites by simultaneous photopolymerization of some urethane monomers and photoinduced formation of gold nanoparticles

Urethane–urea dimethacrylates were synthesized and used in the preparation of nanocomposites containing gold nanoparticles (Au NPs) in situ photogenerated during the UV‐curing process in the absence of reducing agent. A study of the photopolymerization kinetics showed that the photoreactivity of the monomers alone or in combination with a dual urethane benzophenone (BP) macromer is dependent on the nature of photoinitiator (Irgacure819, BP/amine) and the formulation composition. It was found that the addition of 1 wt % AuBr₃ in monomers slightly improved the polymerization rate and the degree of conversion. The formation of Au NPs into the network was confirmed through UV–vis, XRD, EDX, SAXS, and TEM analyses, the last indicating the existence of NPs with size around 8.5 nm and spherical/triangle shapes. On addition of 10 wt % 2[N‐methacryloyloxyethyl‐(N'‐2‐thioethyl)] (urea) in formulation, the Au NPs (200 nm) became predominantly cubic/hexagonal in shape. The composite films emit fluorescence at 575 nm, and this property could be exploited in the field of fluorescent bio/sensors. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 728–738     

Synthesis of highly dispersed,block copolymer‐grafted TiO2 nanoparticles within neat block copolymer films

The objective of the study is to formulate exclusive block copolymer (BCP) nanocomposites by dispersing bcp end‐grafted nanoparticles (bcp‐g‐nps) of PMMA‐b‐PS‐g‐TiO₂ within PS‐b‐PMMA matrix. PMMA‐b‐PS‐g‐TiO₂ is synthesized using a “grafting‐to” approach and characterized by XPS and TGA to establish that the copolymer chains were bonded to NPs. Good dispersion of bcp‐g‐nps in PMMA and PS‐PMMA bcp films is observed, in contrast to poor dispersion in PS films. In PS‐PMMA films, the compatible and identical bcp nature of the end‐grafted polymer, and large NP size caused it to span across entire PS‐PMMA domains. Poor and good dispersion in PS and PMMA matrices, respectively, can be rationalized by the fact that NPs interactions are driven by the PMMA at the outer corona of the bcp‐g‐nps. Developing bcp‐g‐nps as a strategic route to preparation of highly dispersed high permittivity NPs like titanium dioxide (TiO₂) in bcp matrix can have important ramifications for energy storage devices. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 468–478     

Preparation of siloxane‐based urethane dimethacrylates carrying carboxylic groups and the effect of silver nanoparticles on the properties of composite polymer films

This work reports on the synthesis of three acid oligosiloxane‐urethane dimethacrylates and their use to obtain hybrid nanocomposite films, in which the presynthesized silver nanoparticles (NPs) were incorporated before photopolymerization, or produced via in situ photoreduction of the silver nitrate (AgNO₃) precursor into the formulation, without any conventional reducing agent. All samples were characterized by ¹H NMR, FT‐infrared and UV spectroscopies, photodifferential scanning calorimetry (photo‐DSC), transmission electron microscopy (TEM), and energy‐dispersive X‐ray (EDX) analysis. Fourier transformed infrared spectroscopy and photo‐DSC results showed that dimethacrylates having hydrophilic segment of poly(ethylene oxide) type in structure are more reactive than the acid oligosiloxane dimethacrylate. When another urethane dimethacrylate is taken as a comonomer, the photopolymerization rate (0.112–0.132 s^?1) and the degree of conversion (82–93%) significantly increased. Experimental evidence of the existence of nanosilver into the polymer matrix generated upon UV irradiation has been supported by UV spectroscopy, EDX and TEM analysis, the last allowing a visualization of the formation of silver NPs with size between 2 and 15 nm. Mechanical parameters and wettability of the photocrosslinked films are also discussed in the prospect of further potential applications in the biomedical field. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of imidazolium‐functionalized ionic polyurethane and formation of CdTe quantum dot–polyurethane nanocomposites

A series of positively charged imidazolium‐functionalized ionic polyurethanes (IPUs) were prepared in one‐step polymerization process by polymerization of presynthesized short‐chain imidazolium‐based ionic diol, polyethylene glycols with different molecular weights as long‐chain diols, and toluylene‐2,4‐diisocyanate. The structures of IPUs are confirmed by ¹H NMR analysis, and the thermogravimetric analysis measurement indicates that the IPUs have high degradation temperature. Fluorescent nanocrystal–polymer composites CdTe–IPU can be prepared conveniently, by the electrostatic interaction between positively charged IPUs and the negatively charged aqueous CdTe quantum dots (QDs). UV–vis absorption and photoluminescence spectra indicate the photochemical stability and strong fluorescent emission of CdTe–IPU composites. The quantum yields (QYs) of the composites are high and basically restore the QYs of the pure QDs. In addition, the transmission electron microscopy photographs show that the QDs in composites are uniform (about 3 nm in diameter) and monodisperse. The obtained nanocomposites are powder or elastomers with good film building. The casted CdTe–IPU films are transparent under visible light, and the colors of the composites and their films are vivid under a UV lamp. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Polymer–TiO2 composite nanorattles via RAFT‐mediated emulsion polymerization

In this work, successful synthesis of polymer nanorattles containing titanium dioxide pigment particles in the centers of air voids is reported. The method used amphiphilic macro‐RAFT copolymers as stabilizers for pigment dispersion and the subsequent encapsulation of the pigment with polymer. The particles were first encapsulated by a water swellable hydrophilic layer, followed by a hard hydrophobic layer. Nanorattles were formed by swelling of hydrophilic polymer layers on the surface of the encapsulated pigment particles in a basic solution at elevated temperature. After swelling, the outer hard polymer shell was crosslinked to improve its strength. Air void sizes of the nanorattles were found to be controlled by swelling time, temperature, and the hydrophilic polymer layer thickness. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Azobenzene‐containing LC polymethacrylates highly photosensitive in broad spectral range

Two photosensitive chiral liquid crystalline azobenzene‐containing polymethacrylates having different length of flexible spacer connecting chromophores with backbone were synthesized and their phase behavior and photo‐optical properties were studied. Both polymers consist of lateral methyl substituents in ortho‐position of azobenzene chromophores providing high photosensitivity even in red spectral region as well as high thermal stability of photoinduced Z‐form of azobenzene chromophores. It is shown, that smectic phase (SmA*) formation in films of polymer with longer spacer predetermines its quite unusual spectral response to UV and subsequent visible light actions. The SmA* phase promotes spontaneous homeotropic alignment of azobenzene chromophores in polymer films. UV‐irradiation induces not only E‐Z isomerization but also results in disruption of homeotropic alignment, whereas subsequent visible light action enables to obtain films with the low degree of chromophores orientation. The photo‐orientation phenomena under the action of polarized light of different wavelength on polymer films were studied. The possibility of using red polarized light of moderate intensity for optical photorecording on polymer films is demonstrated. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2962–2970     

A versatile preparation of azobenzene‐dye functionalized colored polymer nanoparticles by surface modification

A series of stable and translucent colored nanolatex, that is, colloidal aqueous suspensions of dye‐tagged polymer nanoparticles (NPs) in the 15‐ to 20‐nm diameter range, have been prepared by covalent attachment of azobenzene chromophores to the surface of reactive NPs. Primary crosslinked NPs bearing chlorobenzyl groups were produced by microemulsion copolymerization of styrene and vinylbenzylchloride. Amine‐functionalized NPs were obtained after a second functionalization step with polyamines (cyclam and polypropyleneimine dendrimers of first and third generations). Dye‐doped particles were obtained by reacting pyridylazo‐dimethylaminobenzene (PADA) with chlorobenzyl‐NPs and by reacting amine‐reactive dimethylaminoazobenzene dyes (DABsyl, DAB‐ITC) as well as Disperse Red 1 acrylate with polyamine‐coated NPs. Regardless the dye solubility, the grafting readily proceeded in aqueous suspensions at room temperature in the presence of a cationic surfactant without added solvent. Purple, red, and orange suspensions (maximum absorption around 550, 500, 430 nm), with dye loads ranging from 0.3 to 1.2 mmol/g, corresponding to 400–1800 azobenzene residues per NP, are obtained. The reported results indicate that functional polymer NPs, with remarkably accessible multiple anchoring sites, are useful building blocks. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3375–3386, 2008     

Metal nanocomposite films prepared in situ from PVA and silver nitrate. Study of the nanostructuration process and morphology as a function of the in situ routes

Cast‐hybrid films composed of polyvinyl alcohol (PVA) and silver nitrate were treated according to three different ways, thermal annealing, UV‐irradiation, and chemical reduction by a borohydride solution, to obtain PVA/silver nanocomposite films. The nanostructuration process was studied as a function of the treatment conditions, and discussed as a function of the mobility state of the polymer chains in the nanocomposite matrix during treatment. A homogeneous dispersion of crystalline silver nanoparticles was obtained by thermal annealing above T_g and below T_m and UV‐lamp irradiation below T_g. For these two treatments, the major processing parameters were the annealing temperature and time and the UV‐exposure time, respectively. For low‐conversion rate in Ag(0), the films evolved upon ageing at room temperature. Totally different morphology and Ag(0) conversion were achieved by chemical reduction in a borohydride solution. All the silver ions were reduced into Ag(0), and crystalline silver nanoparticles layers parallel to the film surface were observed after the treatment. This morphology was related to the high‐swollen state of the polymer matrix during treatment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2062–2071, 2008     

Synthesis of azide‐functionalized nanoparticles by microemulsion polymerization and surface modification by click chemistry in aqueous medium

Stable translucent aqueous suspensions of azide‐functionalized cross‐linked nanoparticles (NPs), with diameters in the 15–20 nm range, were prepared using two synthetic approaches. Copolymerization of azidomethylstyrene (VBN₃), styrene, and divinylbenzene in various oil‐in‐water microemulsions led to NPs with modulable azide contents (0.53–0.78 mmol/g) and surface over volume distributions. Surface modifications of reactive NPs bearing chlorobenzyl groups, produced by microemulsion copolymerization of vinylbenzylchloride, with sodium azide led to azido‐coated NPs with high densities of peripheral groups (0.13–0.45 mmol/g). It is shown that the nature of the surfactant used for the preparation of the microemulsion has an impact on the incorporation of VBN₃ in the polymer particles as well as on the surface reaction yield. The azide‐functionalized NPs were used as clickable polymeric scaffolds for the grafting of sparingly water‐soluble dansyl and fluorescein derivatives through copper(I)‐catalyzed azide‐alkyne cycloaddition in water in the presence of surfactants as solubilizing agents to produce fluorescent NPs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

UV‐induced crosslinking of ring opening metathesis block copolymer micelles

Statistical and amphiphilic block copolymers bearing cinnamoyl groups were prepared by ring opening metathesis polymerization (ROMP). The UV‐induced [2 + 2] cycloaddition reaction of polymer bound cinnamic acid groups was studied in polymer thin films as well as in block copolymer micelles. In both cases, exposure to UV‐light for 10 min led to a crosslinking conversion of about 60%, as determined by FT‐IR spectroscopy and UV–vis absorption measurements. Time based IR‐spectroscopy revealed a maximum conversion of 78% reached after an irradiation time of about 16 min. For micelles obtained from polymers bearing 5 mol % or more cinnamoyl groups, the crosslinking reaction proceeded smoothly, yielding in crosslinked particles which were stable in a non‐selective solvent (CHCl₃). Diameters determined by dynamic light scattering in the selective solvent (MeOH) were similar for both, non‐crosslinked and crosslinked micelles, whereas diameters of crosslinked micelles in the non‐selective solvent (CHCl₃) were significantly larger compared to MeOH samples. This strategy of direct self assembly of block‐copolymers in a selective solvent followed by “clean” crosslinking, without the need for additional crosslinking reagents or crosslinking initiators, provides a straight forward approach toward ROMP‐based polymeric nano‐particles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2402–2413, 2008     

Anomalous solubility of polyacrylamide prepared by dispersion (precipitation) polymerization in aqueous tert‐butyl alcohol

Polyacrylamide prepared by dispersion (precipitation) polymerization in an aqueous t‐butyl alcohol (TBA) medium is only partially soluble when the TBA concentrations in the polymerization media are in the range 82 vol % < TBA < 95 vol %. Independent experiments with a soluble (linear) sample of polyacrylamide show that the polymer swells sufficiently in the aforementioned media to lower the glass‐transition temperature of the polymer below the polymerization temperature (50 °C). The anomalous solubility has been attributed to the crosslinking of polymer chains that occurs during the solid‐phase polymerization of acrylamide in the swollen polymer particles. It is postulated that some of the radical centers shift from the chain end to the chain backbone during solid‐phase polymerization by chain transfer to neighboring polymer molecules, and when pairs of such radicals come into close vicinity, crosslinking occurs. However, dispersion (precipitation) polymerization in other media such as aqueous methanol and aqueous acetone yields polymers that are soluble. This result has been attributed to the fact that the polymer radical undergoes a chain‐transfer reaction with these solvents at a much faster rate than with TBA, which overcomes the effect of the polymer‐transfer reaction. Even the addition of as little as 5% methanol to a TBA–water mixture (TBA:water = 85:10) gives rise to a soluble polymer. The chain‐transfer constants for acetone, methanol, and TBA have been determined to be 9.0 × 10^?6, 6.9 × 10^?6, and 1.48 × 10^?6, respectively, at 50 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3434–3442, 2001     

Synthesis and properties of the [2.2]paracyclophane‐containing conjugated polymer with benzothiadiazole as an electron acceptor

A novel donor–acceptor type conjugated polymer based on PPE with [2.2]paracyclophane and benzothiadiazole units in the main chain was synthesized by the Sonogashira coupling reaction. The obtained polymer was quite soluble in common organic solvents, and the transparent and uniform thin film of the polymer was obtained easily by casting or spin‐coating from a toluene solution. The polymer showed an extension of π‐delocalization via the through‐space with π‐π stacking according to the UV–visible (UV–vis) absorption spectra in comparison with that of the model compound. The polymer exhibited orange photoluminescence in solution (fluorescence quantum efficiency = 0.13) and in the solid state. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5891–5899, 2004     

Triplet‐sensitized irradiation of a main‐chain liquid crystalline poly(aryl cinnamate) in three different phases

Visible light irradiation of thin films of a main‐chain liquid crystalline poly(aryl cinnamate) using ketocoumarins as triplet sensitizers leads to photochemical crosslinking and UV‐vis and FTIR spectroscopic changes associated with saturation of the cinnamate double bond, most likely by 2 + 2 photocycloaddition. The triplet sensitizers are themselves photolabile and are lost by photochemical reactions during the sensitization process. A new ketocoumarin sensitizer with decyloxy substituents and a reduced tendency to phase separate from the polymer is reported. A simple calculation of the sensitization stoichiometry shows that a single molecule of this ketocoumarin sensitizes the destruction of approximately 90 cinnamate chromophores in the “as cast” films below T_g and about 300 chromophores in the more‐ordered glassy nematic films and in “as cast” films of poly(vinyl cinnamate). Triplet sensitization of fluid nematic films leads, upon initial irradiation, to UV‐vis hyperchromism that is attributed to disruption of chromophore aggregation and, possibly, to disruption of the nematic mesophase as photoproducts begin to form. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 134–144, 2001     

Effect of oligomers on the polymer diffusion rate in poly(butyl methacrylate) latex films

The aqueous phase of a poly(butyl methacrylate) (PBMA) latex dispersion contained an oligomeric component that was isolated after sedimentation of the PBMA latex particles. The component contained both water‐soluble PBMA oligomer and some longer chain species that were present as a very fine colloidal dispersion. We describe the isolation and characterization of this component. This component was then added to a purified PBMA latex dispersion from which the aqueous component was previously removed. Latex films were prepared, and in the presence of the oligomeric material, the rate of polymer diffusion in the latex film was strongly enhanced. The magnitude of the enhancement was fit quantitatively to the Fujita–Doolittle equation, indicating that the oligomers acted like a traditional plasticizer to increase the free volume in the system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3933–3943, 2000     

Acrylic polymer/silica hybrids prepared by emulsifier‐free emulsion polymerization and the sol–gel process

Acrylic polymer/silica hybrids were prepared by emulsifier‐free emulsion polymerization and the sol–gel process. Acrylic polymer emulsions containing triethoxysilyl groups were synthesized by emulsifier‐free batch emulsion polymerization. The acrylic polymer/silica hybrid films prepared from the acrylic polymer emulsions and tetraethoxysilane (TEOS) were transparent and solvent‐resistant. Atomic force microscopy studies of the hybrid film surface suggested that the hybrid films did not contain large (e.g., micrometer‐size) silica particles, which could be formed because of the organic–inorganic phase separation. The Si? O? Si bond formed by the cocondensation of TEOS and the triethoxysilyl groups on the acrylic polymer increased the miscibility between the acrylic polymer component and the silica component in the hybrid films, in which the nanometer‐size silica domains (particles) were dispersed homogeneously in the acrylic polymer component. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 273–280, 2006     

Network formation of a phenyl vinyl ketone copolymer with 4-vinylbenzil and its photodecrosslinking in films

The irradiation (λ > 400 nm) in air of a copolymer of phenyl vinyl ketone with 4-vinylbenzil (VBZ) containing 1.5 wt % VBZ structural units in film, followed by the thermal decomposition of the resulting pendant benzoyl peroxide groups, leads to crosslinking. The subsequent irradiation of the crosslinked polymer at 366 nm results in the cleavage of the poly(phenyl vinyl ketone) chain between the junction points of the polymer network through a Norrish type II reaction. Therefore, poly(phenyl vinyl ketone-co-4-vinylbenzil) represents a novel type of photoresist based on polymer network decrosslinking. The process involves three steps: photogeneration of peroxide, crosslinking by its thermal decomposition, and subsequent photodecrosslinking of the polymer network. This material provides positive-tone images after UV exposure (λ > 330 nm) and development in an organic medium such as isopropyl methyl ketone. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 765–771, 2004     

Role of adsorbed chain rigidity in reinforcement of polymer nanocomposites

The thermomechanical behavior of polymer nanocomposites is mostly governed by interfacial properties which rely on particle–polymer interactions, particle loading, and dispersion state. We recently showed that poly(methyl methacrylate) (PMMA) adsorbed nanoparticles in poly(ethylene oxide) (PEO) matrices displayed an unusual thermal stiffening response. The molecular origin of this unique stiffening behavior resulted from the enhanced PEO mobility within glassy PMMA chains adsorbed on nanoparticles. In addition, dynamic asymmetry and chemical heterogeneities existing in the interfacial layers around particles were shown to improve the reinforcement of composites as a result of good interchain mixing. Here, the role of chain rigidity in this interfacially controlled reinforcement in PEO composites is investigated. We show that particles adsorbed with less rigid polymers improve the mechanical properties of composites. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 9–14