Interaction of inorganic salts with polar polymers. II. Infrared studies of polymer–inorganic nitrate systems

Certain inorganic nitrate salts are quite soluble in the polymers studied, namely, cellulose acetate, poly(vinyl acetate), poly(vinyl alcohol), poly(methyl methacrylate), and poly(methyl acrylate). Large effects upon the glass-transition temperature were observed in those systems where the transition could be readily measured. Large shifts in the infrared spectra of both the inorganic nitrate salts and in the polymer carbonyl and ester ether frequencies have been observed. These observations have been interpreted in terms of complex formation between these polymers and salts in the solid state. The proposed structure of the complex explains the nature of the infrared shifts both for the nitrate salts and the polymers as well as explaining the concentration effects observed. Effects of the solvating environment upon the salt and polymer spectra remain unexplained. The large glass-transition effects are a result of the degree of solubility of the salts in the polymers and the interactions between them. However, the reason why, in some cases, the change in the transition temperature as a function of concentration goes through a maximum is unclear.     

A different diffusion mechanism for drug molecules in amorphous polymers

Polymer materials are widely used in controlled drug release, and the diffusion property of drug molecules in these materials is of great importance. In this work, the diffusion behavior of a model drug (aspirin) in different ratios of poly(lactic acid-co-ethylene glycol) (PLA-PEG) was investigated by molecular dynamics simulations. Two major factors, which influence the diffusion of aspirin in polymer matrix: the wriggling of the polymer chain and the free volume of the polymer matrix, are discussed. The wriggling of the polymer chain mainly controls the diffusion of aspirin molecules. Free volume becomes the secondary effect. For two different polymers having a similar degree of wriggling, the free volume controls the diffusion of the aspirin molecules. Comparing with the diffusion behavior of small gas molecules in polymer matrix, a different mechanism was proposed for the drug molecules. The drug molecules can only diffuse along with the wriggling of the polymer matrix.     

Polymer nanocomposites with iron oxide nanoparticles

Novel polymer nanocomposites with iron oxide nanoparticles in a poly(1-vinyl-1,2,4-triazole) matrix are promising for the development of new biomedical materials of long-term effect.     

Radiation‐induced fabrication of polymer nanoporous materials from microphase‐separated structure of diblock copolymers as a template

Polymer nanoporous materials with periodic cylindrical holes were fabricated from microphase‐separated structure of diblock copolymers consisting of a radiation‐crosslinking polymer and a radiation‐degrading polymer through simultaneous crosslinking and degradation by γ‐irradiation. A polybutadiene‐block‐poly(methyl methacrylate) (PB‐b‐PMMA) diblock copolymer film that self‐assembles into hexagonally packed poly(methyl methacrylate) cylinders in polybutadiene matrix was irradiated with γ‐rays. Solubility test, IR spectroscopy, and TEM and SEM observations for this copolymer film in comparison with a polystyrene‐block‐poly(methyl methacrylate) diblock copolymer film revealed that poly(methyl methacrylate) domains were removed by γ‐irradiation and succeeding solvent washing to form cylindrical holes within polybutadiene matrix, which was rigidified by radiation crosslinking. Thus, it was demonstrated that nanoporous materials can be prepared by γ‐irradiation, maintaining the original structure of PB‐b‐PMMA diblock copolymer film. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5916–5922, 2007     

Studies on Novel Polymer Materials Prepared through Intermacromolecular Complexation

The basic feature of polymers is their multi-order structure. Structure change at each level offers a possibility tomodify polymer properties and to develop new polymer materials. Therefore,novel polymer materials can be developed by tailoring their chain structure through chemical bonding among atoms, i.e., via the traditional molecular chemistry methods, e.g., polymerization of new monomer, controlling chain length (molecular weight and molecular weight distribution) and stereoregularity, copolymerization of different kinds of monomers, controlling sequence distribution,block of graft length of copolymer, etc., which have been the focus of polymer chemistry for several decades, as well as by tailoring specific supramolecular architecture using molecules as building block through intermolecular interactions, i.e., via supramolecular science methods, e.g., molecular self-assembly, intermacromolecular complexation, etc., which is a modern and fast-developing academic research field.This paper reports novel polymer materials prepared through intermacromolecular complexation,e.g., a new polymer solid electrolyte poly(metyl methacrylate-methacrylic acid)[P(MMA-MAA)]/poly(ethylene oxide) (PEO)/A2-LiClO4 developed by intermacromolecular complexation through hydrogen bonding, which has enhanced ambient ionic conductivity and fairly good mechanical and film-forming properties, a new polymer microcomposite poly(acrylonitrile-acrylamide-acrylic acid) [P(AN-AM-AA)]/poly(vinyl alcohol) (PVA) reinforced by the twin molecular chain microfibrils formed through intermacromolecular complexation of P(AN-AM-AA) with PVA through hydrogen bonding, which exhibits much better mechanical properties than its constituents and could be used to manufacture PVA based complexed fibers with higher modulus and better dyeability, a new polymer flooding agent poly(acrylamide-acrylic acid)[P(AM-AA)]/poly(acrylamide- dimethyldiallylammonium chloride) [P(AM-DMDAAC)] developed by intermacromolecular complexation of the oppositely charged polyions through Coulomb forces,which shows much higher viscosity and better resistance to temperature, shear rate and salt than its constituents, and has potential application in enhanced oil recovery.     

Metal ion doped polymers as media for optical memories

Polymer materials are making an impact on optical storage technology to develop high information density and fast access type memories with a high read-out efficiency. The principle and advantages of three-dimensional (3-D) data storage in the form of interference patterns (holograms) have been outlined. Three different information storage materials have been developed by doping metal ions such as Cr(VI) and Fe(III) in water-soluble polymers, namely poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA), which need no further thermal or chemical treatment. Volume transmission holograms have been recorded in dichromated poly(vinyl alcohol) (DCPVA), ferric chloride doped poly(vinyl alcohol) (FePVA) and dichromated poly(acrylic acid) (DCPAA), with and without an electron donor (dimethyl formamide), and xanthene dyes (fluorescein, eosin Y and Rose Bengal). Different parameters influencing the holographic performance have been optimized to achieve a high real-time diffraction efficiency (～70%). An electron transfer process from the polymer matrix to Cr(VI)/Fe(III), leading to the photocrosslinking of the polymer in the form of an interference pattern, has been suggested as the mechanism of information storage (hologram recording) in these materials.     

Nanocomposites of polymers and metals or semiconductors: Historical background and optical properties

Upon transmission of visible light through composites comprising of a transparent polymer matrix with embedded particles, the intensity loss by scattering is substantially reduced for particle diameters below 50–100 nm (nanoparticles, nanosized particles). As a consequence, related materials (nanocomposites) have found particular interest in optical studies. The first part of this article deals with a historical survey on nanoparticles and nanocomposites and the importance of small particle sizes on their optical properties. The second part focuses on results from our laboratory concerning nanocomposites with extremely high or low refractive indices and dichroic nanocomposites and their application in bicolored liquid crystal displays (LCD). The inorganic colloids required for these studies (lead sulfide, iron sulfides, gold, and silver) were prepared in situ in presence of a polymer or isolated as redispersable metal colloids modified at the surface with a self‐assembled monolayer (SAM) of an alkanethiol. The nanocomposites themselves were finally obtained by coprecipitation, spin coating, solvent casting or melt extrusion, with poly(ethylene oxide), gelatin, poly(vinyl alcohol) and polyethylene as matrix polymers.     

General synthesis of hollow composite ellipsoids

A facile and general approach towards composite hollow ellipsoids has been proposed. The parent polystyrene (PS) hollow spheres are embedded in a matrix, for example, poly(vinyl alcohol), and stretched into the corresponding ellipsoids. The aspect ratio of the ellipsoids is tunable by stretching extent. Accordingly, sulfonated PS hollow ellipsoids are achieved by sulfonation of the PS hollow ellipsoids, which will facilitate an easy complexation with functional materials. Composite hollow ellipsoids, with varied composition ranging between polymer, metal and oxides, and inorganic materials, are synthesized against the polymer ellipsoids as templates. By controlling growth of the functional materials at specific sites, structure of the composite hollow ellipsoids is controlled such as surface-pillared, single-shelled and double-shelled. This approach avoids traditional removal of polymer templates, thus guarantees the shell integrity of the composite hollow ellipsoids.     

Studies on molecular composite. I. Processing of molecular composites using a precursor polymer for poly(p‐phenylene benzobisthiazole)

The blending of a precursor polymer for poly(p‐phenylene benzobisthiazole) (PBZT) with various matrix polymers was attempted, followed by heat conversion of the PBZT precursor polymer to obtain molecular composites consisting of PBZT and the matrix polymers. A higher concentration of mixed solution using organic solvent and milder conditions to remove the solvent could be applied to blend the polymers using the precursor polymer in place of rodlike PBZT. The dispersibility of PBZT in the matrix polymer in the blended materials obtained depended on the ability to form intermolecular hydrogen bridges between the PBZT precursor and the matrix polymer. In particular, the blended material, obtained using a nonthermoplastic aromatic polyamide as the matrix polymer having a molecular structure similar to that of the PBZT prepolymer, was transparent and showed excellent reinforcing efficiency of PBZT. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 189–197, 1999     

The features of absorption of aqueous–organic mixtures by polyurethane–poly(2-hydroxyethyl methacrylate) matrix by the data of NMR spectroscopy

The features of hydration of the interpenetrating polymer network consisting of 83% polyurethane and 17% poly(2-hydroxyethyl methacrylate) as well as the initial polymers are studied by the method of lowtemperature NMR spectroscopy. It is shown that the two-component polymer matrix is capable of absorption of significant amounts of water in the form of clusters, with the size strongly depending on the presence of organic compounds, such as chloroform and trifluoroacetic acid. Thus, the changes in the medium composition allow one to control the state of water absorbed by the polymer in a wide range. The found effect may be used to create materials with the controlled delivery of biologically active substances whose retention by the matrix is determined to a great extent by the energy of binding of water by the polymer.     

Polyethylene-based nanocomposite: Structure and properties of poly(vinyl alcohol)/organofunctionalized Mg-doped fluorapatite hybrid

We report here the production and characterization of polymer nanocomposites (NC)s containing nanoceramics of organofunctionalized Mg-doped fluorapatite (MDFA) in a poly(vinyl alcohol) matrix. First, the MDFA materials were functionalized with N-trimellitylimido-L-leucine modifier through ultrasonic irradiation. The numerous experimental techniques like Fourier transform infrared spectroscopy, X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis were applied to characterize the prepared materials. Thermal analysis of the obtained NCs showed an increase in thermal stability of the NCs when compared to the neat macromolecule.     

Osteoblast culture on bioerodible polymers: studies of initial cell adhesion and spread

The development of systems for the growth of osteoblasts on bioerodible polymeric matrices was explored. Three classes of bioerodible polymers were studied as possible matrix supports for osteoblast growth: the poly(anhydrides), poly(phosphazenes) and poly(lactic acid/glycolic acid) copolymers. Neonatal calvarial cells from Sprague–Dawley rats were seeded onto polymer disks at a density of 1 × 10⁴ cells/cm². Initial attachment and spreading, rate of growth and morphology were determined, and retention of osteoblast-like phenotype was assessed through measurements of alkaline phosphatase activity in the presence and absence of 1,25(OH)₂ vitamin D3. All results were considered relative to tissue culture polystyrene. Cells were found to attach to all polymers at 8 hr post-seeding. By 24 hr, cell numbers on all polymers were found to be decreased, except for poly(lactic acid/glycolic acid). Rat calvarial osteoblasts seeded on poly-(lactic acid/glycolic acid) reached confluency and retained their phenotype. Successful construction of viable osteoblast–bioerodible polymer composite materials, as presented in our study, may find their usefulness as grafts for atrophic non-unions of bone, for healing craniofacial and other defects and for use as prosthetic implants or coatings. Composite systems of osteoblast cultures may also find their usefulness in furthering our understanding of bone differentiation, maturation and metabolism in a matrix environment.     

Nitrate removal of drinking water by means of catalytically active membranes

The reduction of nitrate to nitrogen in aqueous solutions by means of catalytically active membranes has been investigated. A heterogeneous catalyst (Pd/Cu) has been incorporated in a microporous polyetherimide membrane. After saturation with hydrogen nitrate containing water was filtered through these membranes. The nitrate reduction was studied as a function of pH, volume flow and temperature. It could be demonstrated that the catalyst remained active in the polymer matrix. The calculated activation energy for nitrate reduction is indicating that the reaction is dominated by mass transfer and diffusion.     

Effect of hexagonal boron nitride on poly(vinyl phosphonic acid) composite polymer electrolytes for fuel cells

In this work, hexagonal boron nitride nanoparticles were used as inorganic fillers, which increase the mechanical and thermal stabilities as well as the proton conductivity of the proton conducting composite membranes prepared by blending of poly(vinyl phosphonic acid) and hexagonal boron nitride. Thermo gravimetric analysis showed that the polymer electrolyte membranes are thermally stable up to 200°C. Scanning electron microscopy analysis indicated the homogeneous distribution of boron nitride nanoparticles in the polymer matrix. The crystallinity of the membranes was characterized by using X-ray Diffraction. X-ray patterns support semi-crystalline nature of the composite materials.     

Characterization of Engineering Polymers by Dynamic Mechanical Analysis

There is a growing need for the use of polymers in high-strength and engineering applications, and many new materials and composites have been developed to satisfy this need. Traditionally, thermosetting polymers have been employed as high-strength materials, with the incorporation of various fillers or additives to improve shortcomings in strength and temperature performance. Although these materials are largely unrivaled in high-temperature performance, some of the newer engineering thermoplastics, such as poly(ether ether ketone)(PEEK), poly(ether sulfone) (PES), poly(pheny1ene sulfide) (PPS), and the new backbone liquid-crystal polymers are becoming much more widely used. With this widespread use and with the increasing complexity of polymer blends and composites, there is a strong requirement for a universal means of characterizing such materials in terms of mechanical properties and high-temperature performance. A powerful and versatile analytical technique which is capable of application to a very wide range of materials is that of dynamic mechanical spectrometry. This technique can be used to establish basic material relaxation temperatures and frequencies, the modulus and loss behavior, as well as factors such as degree of cure, fder/matrix bonding, and phase separation.     

Lanthanide Luminescence Improvement by Using a Functional Poly(Ionic Liquid) as Matrix and Co‐ligand

A poly(ionic liquid) (BA‐PIL) carrying a benzoic acid group in each repeating unit of the polymer architecture, which has the dual function of acting as a matrix and second ligand, has been developed. Through the incorporation of BA‐PIL with the complex [Ln(hfa)₃] (hfa=hexafluoroacetylacetone) as an emitting precursor, significant luminescence improvement was achieved in the obtained hybrid materials. Confinement of the lanthanide(III) complexes within the rigid chains of the polymer, together with replacement of the coordinated water molecules, are believed to be ascribed to the enhanced optical properties.     

Novel functionally grafted pseudo-semi-interpenetrating networks constructed by reactive linear-dendritic copolymers

This paper describes the synthesis of amphiphilic pseudo-semi-interpenetrating polymer networks (pseudo-semi-IPNs) containing linear poly(styrene) and poly(ethylene glycol) (PEG) cross-linked through monodendritic fragments. A unique feature of the synthetic strategy is the permanent attachment of the linear segment to the PEG network by a transesterification reaction between the hydroxyl groups at both ends of the PEG and peripheral ethyl ester moieties in the monodendron portion of a linear poly(styrene)-dendritic poly(benzyl ether) AB block copolymer. The proceeding of the reaction is monitored by (1)H NMR and size exclusion chromatography (SEC). The formation of an interlock structure between the linear block and the network matrix in the pseudo-semi-IPN is evidenced by the results from spectroscopic analyses and differential scanning calorimetry measurements. The accessibility of functional centers in the grafted semi-IPN is confirmed by model reactions with fluorescent markers, fluorescence spectroscopy, and NMR techniques and shows the potential of these novel materials as sequestering reagents for resin capture-release applications in parallel synthesis, combinatorial chemistry, and advanced drug design.     

Functional inorganic nanofillers for transparent polymers

The integration of inorganic nanoparticles into polymers has been used for the functionalization of polymer materials with great success. Whereas in traditional polymer composites, micron sized particles or agglomerates typically cause significant light scattering hampering optical applications, in nanocomposites the particle dimensions are small enough for the production of highly transparent composites. A challenge for the generation of such materials is to develop an integrated synthesis strategy adapting particle generation, surface modification and integration inside the polymer. Surface grafting using polymerizable surfactants or capping agents allows for linking the particles to the polymer. Novel techniques such as in situ polymerization and in situ particle processing are beneficial to avoid aggregation of inorganic particles inside the polymer matrix. The functions associated with inorganic fillers are widespread. Layered silicates and related materials are nowadays commercially available for improving mechanical and barrier properties in packaging. With the availability of highly transparent materials, the focus has shifted towards optical functions such as luminescence and UV-protection in transparent polymers. IR-active fillers are used in laser-holography for transparent poly(methyl methacrylate) (PMMA) nanocomposites. Refractive index modulation and ultrahigh refractive index films were developed based on inorganic materials such as PbS. The integration of magnetic nanoparticles has a great potential for applications such as electromagnetic interference shielding and magneto-optical storage.This tutorial review will summarize functions associated with the integration of inorganic nanofillers in polymers with a focus on optical properties.     

Synthesis of poly(1.4.-benzamide) in solutions of randomly coiled polymers

The polycondensation of p-aminobenzoic acid by the use of triphenylphospine and hexachloroethane is described. One way to obtain a mixed solution of rigid rod and flexible coil polymers is the polycondensation of the rigid chains in a solution of a flexible polymer matrix. Results on matrix polycondensation of poly(p-benzamide) in solutions of poly(methyl methacrylate), poly(methyl methacrylate-co-styrene), polystyrene and polyacrylonitrile are reported. It is shown that there exists an interrelation between the phase behavior of the mixed polymer solutions and the influence of the matrix polymer on the synthesis of poly(1.4.-benzamide). The ternary phase diagrams of the rigid rod/flexible coil polymer solutions were determined.     

Effects of ceramic filler in poly(vinyl chloride)/poly(ethyl methacrylate) based polymer blend electrolytes

Effects of nano-ceramic filler titanium oxide (TiO₂) have been investigated on the ionic conductance of polymeric complexes consisting of poly(vinyl chloride) (PVC)/poly(ethyl methacrylate) (PEMA), and lithium perchlorate (LiClO₄). The composite polymer blend electrolytes were prepared by solvent casting technique. The TiO₂ nanofillers were homogeneously dispersed in the polymer electrolyte matrix and exhibited excellent interconnection with PVC/PEMA/PC/LiClO₄ polymer electrolyte. The addition of TiO₂ nanofillers improved the ionic conductivity of the polymer electrolyte to some extent when the content of TiO₂ is 15 wt%. The addition of TiO₂ also enhanced the thermal stability of the electrolyte. The changes in the structural and complex formation properties of the materials are studied by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The scanning electronmicroscope image of nano-composite polymer electrolyte membrane confirms that the TiO₂ nanoparticles were distributed uniformly in the polymer matrix.