Heterogeneous reactions of singlet molecular oxygen with solid polymers

The effect of gas-phase singlet molecular oxygen (¹ΔO₂) upon several solid polymers was investigated by using electron paramagnetic resonance, infrared spectroscopy, and chemical detection techniques. The study was performed by use of ¹ΔO₂ produced by microwave discharge. The application of this method to polymer studies was closely examined. The saturated-chain polymers polystyrene, polyurethane, and polyethylene were found to be inert within the experimental conditions to reaction with ¹ΔO₂, while the unsaturated polymers cis-polybutadiene, trans-polybutadiene, and trans-polyisoprene were found to react quite readily in an apparently surface or near-surface limited reaction to produce hydroperoxide and/or peroxide groups. The introduction by homogeneous mixing of some known metal-chelate ¹ΔO₂ quenchers into the polymer trans-polyisoprene appeared to significantly decrease the rate of oxidation observed.     

Head-to-head vinyl chloride–vinyl acetate copolymer

Addition chlorination of cis-1,4-polybutadiene in the presence of acetic acid as a cosolvent resulted in the formation of head-to-head vinyl chloride–vinyl acetate copolymer. Chlorine analysis, IR, and NMR spectra of the chlorinated polybutadiene indicated that reaction was primarily double bond addition; there was little evidence for substitutive chlorination. Acetate was incorporated by nucleophilic participation of the acetic acid cosolvent. The extent of incorporation of the acetate group in the polymer chain was a function of the acetic acid concentration. Both the glass transition temperatures and the densities of the chloroacetylated polymers decreased as the degree of acetylation increased.     

Reaction between ethanol and silicon–hydrogen of poly(p-vinylphenyldimethylsilane)

A kinetic approach to the polymer reaction, with KOH as catalyst, between ethanol and poly(p-vinylphenyldimethylsilane) containing silicon–hydrogen as a functional group on the side chain was carried out. The rate equation was obtained by measuring the initial rate of the model reaction as v = k[KOH] [SiH] [EtOH] in benzene and v = k[KOH] [SiH] in methyl ethyl ketone. It was observed that the rate of reaction was affected by the polarity of the solvents. In the polymer reaction the rate constant decreased markedly with increasing ethanol concentration. A change of viscosity of the polymer in various solvents was observed to have a good correlation with the decrease in reaction rate in corresponding solvents. In mixed solvents, consisting of both good and poor solvents for the polymers, the reaction rate depended upon two factors, the entanglement of the polymer chain and the polarity of the solvents. The equivalent globular model of the polymer chain is suggested for study of the polymer reaction. A schematic local-distribution curve of the reaction species is proposed.     

Effect of chain interpenetration on polymer–polymer interaction in solution

Two series of monodisperse polystyrenes have been prepared with a molecular weight range of 3,000 to 300,000. One series was lightly substituted with dimethylbenzylamine groups, the other with 2,6 dinitro-4-benzoyloxyphenol groups. Members of each series were dissolved together in benzene solution in the range of 0.1–30%, and the equilibrium constant for the formation of the ammonium phenolate ion pair measured. Also measured was the corresponding equilibrium constant between comparable small molecular weight analogs, and between these analogs and the substituted polymers. The degree of association found between the models and between the models and the polymers was independent of molecular weight, but deviations were found in the polymer–polymer interaction. Normal equilibrium constants were found at high polymer concentrations indicating that chain interpenetration occurred freely. At low concentrations of polymer, if several links per chain were possible it was found an excess of linkages were formed. If only one link per chain was possible, low degrees of association were found for high molecular weight polymers, but the effect was not as large as a consideration of excluded volumes on a spherical model would predict.     

Facile synthesis of comb,star, and graft polymers via reversible addition–fragmentation chain transfer (RAFT) polymerization

Reversible addition–fragmentation chain transfer (RAFT) polymerization has been shown to be a facile means of synthesizing comb, star, and graft polymers of styrene. The precursors required for these reactions were synthesized readily from RAFT‐prepared poly(vinylbenzyl chloride) and poly(styrene‐co‐vinylbenzyl chloride), which gave intrinsically well‐defined star and comb precursors. Substitution of the chlorine atom in the vinylbenzyl chloride moiety with a dithiobenzoate group proceeded readily, with a minor detriment to the molecular weight distribution. The kinetics of the reaction were consistent with a living polymerization mechanism, except that for highly crowded systems, there were deviations from linearity early in the reaction due to steric hindrance and late in the reaction due to chain entanglement and autoacceleration. A crosslinked polymer‐supported RAFT agent was also prepared, and this was used in the preparation of graft polymers with pendant polystyrene chains. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2956–2966, 2002     

A novel synthesis of linear high-molecular-weight poly(4-vinylphenol) and poly[styrene-co-(4-vinylphenol)]

A novel synthesis of linear high-molecular-weight poly(4-vinylphenol) (PVPh) and poly[styrene-co-(4-vinylphenol)] (STVPh, 2 ) via demethylation reaction is developed. The parent polymers, poly(4-methoxystyrene) and poly[styrene-co-(4-methoxystyrene)] produced by free-radical polymerization, are converted to PVPh and STVPh ( 2 ), respectively, by being treated with trimethylsilyl iodide (TMSI) at room temperature. Both ¹H NMR and ¹³C NMR data show that methoxy is completely cleaved and converted to hydroxy after hydrolysis without crosslinking and other side reactions. In addition, size-exclusion chromatography data show that no chain scission occurs during group conversion.     

Spontaneous film formation from a polymer solution

An unusual continuous film formation process of lateral pentyloxy substituted poly(p-phenylene terephthalate)s (s-PPPT) and poly(carbonate) (PC) is observed. A liquid film of polymer solution creeps over the surface of water dropped into the polymer solution. By vaporization of the solvent a solid polymer film is formed on the water surface and can be removed. The driving force for the film formation mechanism is assumed by the reduction of the surface tension of water. Experiments verify this mechanism by increasing the film formation speed using a gas stream, by reducing the formation speed through lowering the surface tension by rinsing agents, and by lowering the solubility of the polymer. As expected, no effects are found by variation of the pH-value of water. Necessary conditions for the film formation process are: good solubility of the polar polymers in organic solvents having a high vapor pressure, complete phase separation, solution density higher than water density, and a surrounding gas phase unsaturated with solvent vapor.The thickness of the mechanically stable films is less than 0.5 m. The films are amorphous by microscopical, FT-IR, x-ray, and DTA investigations.     

In vitro antibacterial and antifungal assay of poly‐(ethylene oxamide‐N,N′‐diacetate) and its polymer–metal complexes

A new polyester, poly‐(ethylene oxamide‐N,N′‐diacetate) (PEODA), containing glycine moiety was synthesized by the reaction of oxamide‐N,N′‐diacetic acid and ethylene glycol and its polymer–metal complexes were synthesized with transition metal ions. The monomer oxamide‐N,N′‐diacetic acid was prepared by the reaction of glycine and diethyl oxalate. The polymer and its metal complexes were characterized by elemental analysis and other spectroscopic techniques. The in vitro antibacterial activities of all the synthesized polymers were investigated against some bacteria and fungi. The analytical data revealed that the coordination polymers of Mn(II), Co(II) and Ni(II) are coordinated with two water molecules, which are further supported by FTIR spectra and TGA data. The polymer–metal complexes showed excellent antibacterial activities against both types of microorganisms; the polymeric ligand was also found to be effective but less so than the polymer–metal complexes. On the basis of the antimicrobial behavior, these polymers may be used as antifungal and antifouling coating materials in fields like life‐saving medical devices and the bottoms of ships. Copyright © 2007 John Wiley & Sons, Ltd.     

Synergistic mechanical response in blends of diene polymers and their complexes with palladium chloride

The mechanical properties of atactic 1,2-polybutadiene and 3, 4-polyisoprene can be modified significantly with the addition of bis(acetonitrile)dichloropalladium(II). These weak rubbery polymers are transformed into glassy materials when the salt concentration is ≅ 4 mol %, in the absence of high-temperature annealing. Stress-strain measurements and Fourier transform infrared (FTIR) spectra for blends of cis-polybutadiene and PdCl₂, without high-temperature annealing, suggest that π-complexes form between palladium and the olefinic groups within the backbone of the polymer. These solid complexes cannot be dissolved in the original solvent (tetrahydrofuran), nor can they be disrupted by triphenylphosphine. Young's modulus of the cis-polymer is enhanced by a factor of 50 when the salt concentration is 4 mol %, and the fracture strain is approximately 300%. An exothermic process centered at ≅ 250°C accompanied by minimal weight loss suggests that PdCl₂ could trigger high-temperature dimerization reactions of the carbon–carbon double bonds in the backbone of the cis-polymer. High-temperature annealing effects on the stress-strain response of cis-polybutadiene with 4 mol % PdCl₂ are consistent with the data from calorimetry, suggesting that catalytically induced chemical crosslinking is operative at high temperatures. This latter claim is verified by infrared spectroscopy at ambient and elevated temperatures. Hence, bis(acetonitrile)dichloropalladium(II) coordinates to and catalyzes dimerization reactions of olefinic groups when they are present in the main chain or the sidegroup. This square-planar transition-metal salt also enhances the high-strain mechanical response of commercial styrene-butadiene-styrene triblock copolymers (Kraton^TM D series). Reactive blending and compatibilization with transition-metal salts are attractive strategies to modify the mechanical properties of commercially important diene-based polymers that contain unsaturation in the main chain or the sidegroup. © 1996 John Wiley & Sons, Inc.     

Properties of a nanocomposite polymer electrolyte from an amorphous comb-branch polymer and nanoparticles

Three fully amorphous comb-branch polymers based on poly(styrene-co-maleic anhydride) as a backbone and poly(ethylene glycol) methyl ether of different molecular weights as side chains were synthesized. SiO₂ nanoparticles of various contents and the salt LiCF₃SO₃ were added to these comb-branch polymers to obtain nanocomposite polymer electrolytes. The thermal and transport properties of the samples have been characterized. The maximum conductivity of 2.8×10^–4 S cm^–1 is obtained at 28 °C. In the system the longer side chain of the comb-branch polymer electrolyte increases in ionic conductivity after the addition of nanoparticles. To account for the role of the ceramic fillers in the nanocomposite polymer electrolyte, a model based on a fully amorphous comb-branch polymer matrix in enhancing transport properties of Li⁺ ions is proposed.     

Investigation of polymer–solvent interactions in poly(styrene sulfonate) thin films

The swelling behavior of acid form poly(styrene sulfonate) (PSS‐H) thin films were investigated using in situ spectroscopic ellipsometry (SE) to probe the polymer–solvent interactions of ion‐containing polymers under interfacial confinement. The interaction parameter (χ), related to the polymer and solvent solubility parameters in the Flory–Huggins theory, describes the polymer‐solvent compatibility. In situ SE was used to measure the degree of polymer swelling in various solvent vapor environments, to determine χ for the solvent‐PSS‐H system. The calculated solubility parameter of 40–44 MPa^1/2 for PSS‐H was determined through measured χ values in water, methanol, and formamide environments at a solvent vapor activity of 0.95. Flory–Huggins theory was applied to describe the thickness‐dependent swelling of PSS‐H and to quantify the water‐PSS‐H interactions. Confinement had a significant influence on polymer swelling at low water vapor activities expressed as an increased χ between the water and polymer with decreasing film thickness. As the volume fraction of water approached ～0.3, the measured χ value was ～0.65, indicating the water interacted with the polymer in a similar manner, regardless of thicknesses. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1365–1372     

Preliminary toxicological studies of selected water‐soluble polymer–platinum conjugates

The objective of this preliminary investigation of a number of water‐soluble carrier‐bound platinum(II) complexes for potential use in cancer chemotherapy was to assess the toxicological behavior of representative platinum coordination compounds anchored to, or incorporated into, polymeric carriers via polymer‐attached amine ligands. The conjugates included linear polyaspartamides (1–4, 6, 7), each composed of a major fraction of subunits featuring side‐chain‐attached tertiary amino groups as water‐solubilizing entities, and a minor fraction of subunits comprising the anchored platinum complexes, again as side‐chain components. Whereas in 1–4 the platinum atom was polymer‐bound through a single amino group, both 6 and 7 contained polymer‐attached cis‐diamine‐chelating ligands coordinating to the metal center. Also included in this study was a linear polyamidoamine (5), which contained a poly(ethylene oxide) segment in the backbone in addition to intrachain ethylenediamine segments acting as cis‐diamine chelating ligands for coordination to the platinum center. The compounds were injected as aqueous (phosphate‐buffered saline) solutions into the tail veins of CD‐1 mice (four to eight mice per conjugate), and the maximally tolerated dose was determined for each compound. For polyaspartamides 1–4 the dose levels ranged from about 25 mg Pt (kg body weight⁻¹) (in conjugate 4) to 500 mg Pt kg⁻¹ (in compound 1), the latter conjugate proving some 100‐fold less toxic than cisplatin (3–4 mg Pt kg⁻¹), which was included in this study for comparison. Low toxicity (tolerated dose 160 mg Pt kg⁻¹) was also observed for the intrachain cis‐diamineplatinum complex polymer (5). The polyaspartamide conjugates 6 and 7, on the other hand, both characterized by a cis‐diamineplatinum complex system in the side chain, were toxic even below the dose level of 20–25 mg Pt kg⁻¹. The preliminary findings of this study, while providing a basis for more extensive and broad‐based toxicological studies, will serve to direct and optimize structural conjugate designs in forthcoming synthetic programs. Copyright © 2000 John Wiley & Sons, Ltd.     

Conformational energy contribution to the heat of solution in polymer–solvent systems. Part II. Experimental results

Heats of solution (ΔH_exp) in solvents of increasing thermodynamic power have been measured for four polymers: polystyrene (PS), poly(vinyl acetate) (PVAc), polyisobutylene (PIB) and polydimethylsiloxane (PDMS). After subtraction from ΔH_exp of an interaction term (calculated by the Hildebrand treatment based on solubility parameters) and the excess volume term, the quantity remaining is interpreted as the conformational energy contribution (ΔU_conf) to the heat of solution. ΔU_conf appears to correlate well with some basic conformational properties of the chain, such as the sign of the temperature coefficient of unperturbed dimensions derived from solution properties, and shows a monotonic behavior with α, the expansion coefficient of the polymer coil in the final solution. Numerical values of ΔU_conf, at least for those cases in which polymer solubility parameters are known with some certainty, are much larger than those evaluated from rubber elasticity experiments (through the experimentally accessible value of the energy component of the force of retraction im simple elongation).     

Energy transfer through heterogeneous dyes‐substituted fluorene‐containing alternating copolymers and their dual‐emission properties in the films

We report synthesis of the modified fluorene polymers tethered to the heterogeneous types of the fluorescent dyes at the cardo carbon for obtaining the dual‐emissive solid materials. A series of the alternating fluorene copolymers modified with pyrene or 9,10‐diphenylanthracene and BODIPY at the cardo carbon based on the red‐emissive donor–acceptor structure were prepared, and their characteristics were examined. From the measurements of the optical properties, the energy transfer efficiencies were evaluated. In summary, variable energy transfer efficiencies were observed between the side chains and from the side chain to the main chain. It was indicated that the energy transfer efficiencies were strongly depended on the types of the energy donor and the detection conditions as such in the solution or film. Furthermore, it was found that the cardo fluorene units can contribute to the suppression of the energy transfer in the condensed state. Finally, the dual‐emissive polymers were obtained in the film states. This is the first example, to the best of our knowledge, not only to offer systematic information on the energy transfer between the dye molecules and the polymer main‐chains via the cardo structure but also to demonstrate the polymer‐based optical materials with the dual‐emission properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2026–2035     

Switching of the helical polymer conformation in a solid polymer film

A chiral photochromic polyisocyanate was incorporated into a solid polymer matrix of poly(methyl methacrylate) (PMMA), yielding an isotropic polymer film. Isomerization of the chiral photochromic azo side groups (cis‐trans) triggers a reversible conformational change of the helical polyisocyanate backbone. Thus the chirooptical properties of the film can be switched photochemically. The isomerization of the helix is much slower than the isomerization of the azo side groups. Below T_g , the photochemically modified helix conformation is thus stable, despite thermal relaxation of the azo chromophores.     

Hydrolytic degradation of poly(rac‐lactide) and poly[(rac‐lactide)‐co‐glycolide] at the air–water interface

The understanding of the simultaneous transport and chain‐scission phenomena involved in the hydrolysis of bulk‐degrading polymers requires the experimental separation of chain cleavage and water diffusion. The hydrolytic chain cleavage of poly(rac‐lactide) rac‐(PLA) and poly[(rac‐lactide)‐co‐glycolide] (PLGA) is analysed on the basis of monolayer degradation experiments combined with an improved data reduction procedure. Different, partly contradictory models of the hydrolytic degradation and erosion mechanism of PLA and PLGA, namely random chain scission and chain‐end scission, are discussed in the literature. The instantaneous linear area reduction observed for the polymer Langmuir films indicates a chain‐end scission mechanism. As monolayers of end‐capped and non‐end‐capped polymers degrade with exactly the same rate, the observed differences in the degradation kinetics of bulk samples do clearly result from differences in the water penetration into these polymers. A pronounced ‘auto‐inhibition’ effect is observed for the polymers degraded at initially high pH of the aqueous subphase in the absence of buffers. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of polymer architecture on self‐diffusion of LC polymers

Two LC side‐group poly(methacrylates) were synthesized, and their melt dynamics were compared with each other and a third, main‐chain side‐group combined LC polymer. A new route was developed for the synthesis of the poly(methacrylate) polymers which readily converts relatively inexpensive perdeuteromethyl methacrylate to other methacrylate monomers. Self‐diffusion data was obtained through the use of forward recoil spectrometry, while modulus and viscosity data were measured using rotational rheometers in oscillatory shear. Diffusion coefficients and complex viscosity were compared to previous experiments on liquid crystal polymers of similar architecture to determine the effect of side‐group interdigitation and chain packing on center of mass movement. The decyl terminated LC side‐group polymer possessed an interdigitated smectic phase and a sharp discontinuity in the self‐diffusion behavior at the clearing transition. In contrast, the self‐diffusion behavior of the methyl terminated LC side‐group polymer, which possessed head‐to‐head side‐group packing, was seemingly unaffected by the smectic–nematic and nematic–isotropic phase transitions. The self‐diffusion coefficients of both polymers were relatively insensitive to the apparent glass transition. The presence of moderately fast sub‐T_g chain motion was supported by rheological measurements that provided further evidence of considerable molecular motion below T_g. The complex phase behavior of the combined main‐chain side‐group polymer heavily influenced both the self‐diffusion and rheological behavior. Differences between the self‐diffusion and viscosity data of the main‐chain side‐group polymer could be interpreted in terms of the defect structure. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 405–414, 1999     

Synthesis and comparison of the structure–property relationships of symmetric and asymmetric water‐soluble poly(p‐phenylene)s

Sodium salts of water‐soluble polymers poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(hexyloxy)‐1,4‐phenylene]} ( P1 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dodecyloxy)‐1,4‐phenylene]} ( P2 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dibenzyloxy)‐1,4‐phenylene]} ( P3 ), poly[2‐hexyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P4 ), and poly[2‐dodecyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P5 )] were synthesized with Suzuki coupling reactions and fully characterized. The first group of polymers ( P1 – P3 ) with symmetric structures gave lower absorption maxima [maximum absorption wavelength (λ_max) = 296–305 nm] and emission maxima [maximum emission wavelength (λ_em) = 361–398 nm] than asymmetric polymers P4 (λ_max = 329 nm, λ_em = 399 nm) and P5 (λ_max = 335 nm, λ_em = 401 nm). The aggregation properties of polymers P1 – P5 in different solvent mixtures were investigated, and their influence on the optical properties was examined in detail. Dynamic light scattering studies of the aggregation behavior of polymer P1 in solvents indicated the presence of aggregated species of various sizes ranging from 80 to 800 nm. The presence of alkoxy groups and 3‐sulfonatopropoxy groups on adjacent phenylene rings along the polymer backbone of the first set hindered the optimization of nonpolar interactions. The alkyl chain crystallization on one side of the polymer chain and the polar interactions on the other side allowed the polymers ( P4 and P5 ) to form a lamellar structure in the polymer lattice. Significant quenching of the polymer fluorescence upon the addition of positively charged viologen derivatives or cytochrome‐C was also observed. The quenching effect on the polymer fluorescence confirmed that the newly synthesized polymers could be used in the fabrication of biological and chemical sensors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3763–3777, 2006