Synthesis of new environmentally friendly poly(urethane-imide)s as an adsorbent including β-cyclodextrin cavities and attached to iron nanoparticles for removal of gram-positive and gram-negative bacteria from water samples

The presence of pathogenic bacteria in water is one of the important health concerns in the world. Herein, we report a new high-performance environmentally friendly poly (urethane-imide) (PUIm) containing β-cyclodextrin (β-CD) in its backbone to adsorb bacteria from water samples with significant heat resistance. New PUIm was prepared by bonding a diisocyanate as a new cross linking agent to β-CD and magnetic nanoparticles (MNPs). The effects of concentrations of bare polymer and polymer bounded to iron nanoparticles and contact times on the adsorption of staphylococcus aureus and Escherichia coli were considered at physiological pH. The adsorption capacity of this polymer is increased by binding it to MNPs and in addition it is possible to separate the polymer from aqueous sample with external magnetic field. A filter was also provided from polymer attached to iron nanoparticles and high percentages of bacteria were removed after filtering the real wastewater.     

Synthesis and degradation behavior of poly(ethyl cyanoacrylate)

Poly(ethyl cyanoacrylate) was synthesized using N,N′-dimethyl-p-toluidine as an initiator through an anionic/zwitterionic pathway. The degradability and the degradation mechanism of the prepared polymer were examined from various viewpoints. A combination of TGA and GPC analysis allowed us to confirm that the thermal degradation of this polymer was predominantly due to an unzipping depolymerization process initiated from the polymer chain terminus. The polymer was inherently unstable and exhibited interesting degradation behavior in solution with basic reagents. The degradation in solution was also found to be attributed to the unzipping of the monomer from the chain end. However, the degradation behavior of the polymer could be controlled by changing solvents, temperatures, and additives. These findings give an insight into the degradation behavior of poly(alkyl cyanoacrylate)s, which is a crucial point in utilizing these polymer homologues for various applications.     

Synthesis of optically active polymers using P-chiral bisphosphines as anionic initiators

Anionic polymerization of triphenylmethyl methacrylate was performed by using P-chiral bisphosphine initiators. According to the optical rotation analysis and circular dichroism measurements, the polymer obtained by using the initiator (S,S)-1,2-bis(boranato(tert-butyl)methylphosphino) ethane exhibited one-handed helical conformation induced by the chirality of phosphorus atoms in the polymer terminal. The enantiomer (R,R)-1,2-bis(boranato(tert-butyl)methylphosphino) ethane gave the opposite one-handed helical polymer. Optically active bisphosphine (S,S)-1,2-bis(boranatomethylphenylphosphino) ethane was employed for the helix-sense-selective polymerization of triphenylmethyl methacrylate in order to obtain the polymer with the same helix sense as the polymer obtained from the initiator (S,S)-1,2-ethane bis(t-butylm-ethylphosphineborane). Further, removal of the coordinated boranes and complexation with platinum(II) on the chiral phosphorus atoms were carried out in order to yield the corresponding polymer-platinum(II) complex without loss of its chiral higher-ordered structure.     

Viscometric study of poly(vinyl chloride)/poly(vinyl acetate) blends in various solvents

The intermolecular interactions between poly(vinyl chloride) (PVC) and poly(vinyl acetate) (PVAc) in tetrahydrofuran (THF), methyl ethyl ketone (MEK) and N,N^′-dimethylformamide (DMF) were thoroughly investigated by the viscosity measurement. It has been found that the solvent selected has a great influence upon the polymer-polymer interactions in solution. If using PVAc and THF, or PVAc and DMF to form polymer solvent, the intrinsic viscosity of PVC in polymer solvent of (PVAc+THF) or (PVAc+DMF) is less than in corresponding pure solvent of THF or DMF. On the contrary, if using PVAc and MEK to form polymer solvent, the intrinsic viscosity of PVC in polymer solvent of (PVAc+MEK) is larger than in pure solvent of MEK. The influence of solvent upon the polymer-polymer interactions also comes from the interaction parameter term Δb, developed from modified Krigbaum and Wall theory. If PVC/PVAc blends with the weight ratio of 1/1 was dissolved in THF or DMF, Δb<0. On the contrary, if PVC/PVAc blends with the same weight ratio was dissolved in MEK, Δb>0. These experimental results show that the compatibility of PVC/PVAc blends is greatly associated with the solvent from which polymer mixtures were cast. The agreement of these results with differential scanning calorimetry measurements of PVC/PVAc blends casting from different solvents is good.     

Dynamic Light Scattering Characterization of a Water-Soluble Terpolymer with Vinyl Biphenyl in Unsalted and Brine Solutions

The sizes and distributions of polymer chains and associating aggregates, hydrophobic associations, and apparent viscosities were investigated with dynamic light scattering (DLS), fluorescence spectroscopy and viscometry for the hydrophobically associating terpolymer poly[acrylamide(AM)/vinyl biphenyl(VP)/sodium 2-acrylamido-2-methylpropane sulphonate(NaAMPS)] (PAAP) in unsalted and brine solutions. The effects of polymer, NaCl concentration, and temperature on the conformation of polymer chains and the formation of associating structures in aqueous solutions were studied. Intra- and inter-molecular hydrophobic associations were formed and the polymer chains were coiled in unsalted solutions below a critical association concentration (C _p *): 0.05 g·dL^?1, and the apparent viscosity was very low and varied slightly with polymer concentration, but a large number of large aggregates were formed because of the presence of dominant intermolecular associations above C _p *, and the apparent viscosity increased abruptly with increasing polymer concentration. The PAAP chains were comparatively expanded (R _h: 21–92 nm) in brine solutions, resulted from the simultaneous incorporation of the bulky pendant side groups, including the biphenyl and 2-acrylamido-2-methylpropane sulphonate groups. With the addition of NaCl, large associative aggregates in unsalted solutions were destroyed to form comparatively expanded mono-macromolecules and smaller aggregates. However, as the NaCl concentration was increased from to 15 to 80 g·L^?1, more large aggregates were again formed, leading to the obvious salt-thickening behavior. The variation of R _h with temperature proved that intermolecular hydrophobic association is an endothermic process.     

Enantioselective polymer prepared by surface imprinting technique using a bifunctional molecule

An enatioselective surface-imprinted polymer for an amino acid derivative (N-benzyloxycarbonyl-glutamic acid, Z-Glu) was prepared using the bifunctional molecule, benzyldimethyl-n-tetradecylammonium chloride (Zeph). The long-chain quaternary ammonium chloride was found to serve the dual function of an emulsifier and host molecule, while conventional functional molecules possess only the latter function. Chiral recognition ability and ligand specificity of the imprinted polymer were demonstrated by several batchwise tests using different four amino acid derivatives. The surface-imprinted polymer could recognize the chirality of N-protected glutamic acid; therefore, it preferentially adsorbed the corresponding enantiomer that was imprinted in the preparation. The pH and buffer concentration in the aqueous solution are the key factors enhancing enantioselectivity. The molecularly imprinted polymer could distinguish the specific structure from other molecular analogues, even though the structural difference was the only methylene group. The high interfacial activity of the functional molecule and the low swelling property of the imprinted polymer were important in ensuring high imprinting effect. The mechanism of chiral recognition on the polymer was also discussed.     

Preparation of ionic liquid-encapsulated polymer particles

Encapsulation of ionic liquid, 1-hexyl-3-methylimidazolium bis(trifluoromethane sulfonyl)amide ([Hmim][TFSA]), was carried out by microsuspension polymerization of ethylene glycol dimethacrylate (EGDM) utilizing the self-assembling of phase-separated polymer method, which had been proposed by us for the preparation of hollow polymer particles. After the optimization of the polymerization conditions, ionic liquid-encapsulated polymer particles, which have smooth surface morphology and a single hollow structure, were successfully prepared. Encapsulation efficiency of [Hmim][TFSA] was significantly improved from about 20–70 % by changing the shell polymer from polyEGDM homopolymer to poly(EGDM-butyl methacrylate) (50/50, w/w) copolymer, which was likely to have relatively low affinity for [Hmim][TFSA]. Additionally, ionic liquid-encapsulated polymer particles displaying ionic conductivity were successfully prepared using triethylene glycol dimethacrylate as divinyl monomer instead of EGDM.     

Glucose-Mediated Insulin Release Carrier

Polyacrylic acid-co-methacrylamidophenylboronic acid) (PAA-co-PMAAPBA) copolymers were prepared using different concentrations of 3-methacrylamidophenylboronic acid (MAAPBA). The release of insulin from the insulin loaded polymer is dependent on the composition between acrylic acid and MAAPBA in the copolymer. With an increase in concentration of 3-methacrylamidophenylboronic acid, the glucose responsive insulin release from polyacrylic acid-co-methacrylamidophenylboronic acid) polymer at the physiological pH of 7.4 was enhanced. The presence of glucose resulted in disintegration of the polymer leading to release of the loaded insulin.     

Chiral polymer hosts for circularly polarized electroluminescence devices

Polymer electroluminescence devices producing circularly polarized luminescence (CP PLEDs) have valuable photonic applications. The fabrication of a CP PLED requires a polymer host that provides the appropriate chiral environment around the emitting dopant. However, chemical strategies for the design of chiral polymer hosts remain underdeveloped. We have developed new polymer hosts for CP PLED applications. These polymers were prepared through a free-radical polymerization of 3-vinylcarbazole with a chiral N-alkyl unit. This chiral unit forces the carbazole repeat units to form mutually helical half-sandwich conformers with preferred (P)-helical sense along the polymer main chain. Electronic circular dichroism measurements demonstrate the occurrence of chirality transfer from chiral monomers to achiral monomers during chain growth. The (P)-helical-sense-enriched polymer interacts diastereoselectively with an enantiomeric pair of new phosphorescent (R)- and (S)-dopants. The magnitude of the Kuhn dissymmetry factor (g_abs) for the (P)-helically-enriched polymer film doped with the (R)-dopant was found to be one order of magnitude higher than that of the film doped with the (S)-dopant. Photoluminescence dissymmetry factors (g_PL) of the order of 10⁻³ were recorded for the doped films, but the magnitude of diastereomeric enhancement decreased to that of g_abs. The chiral polymer host permits faster energy transfer to the phosphorescent dopants than the achiral polymer host. Our photophysical and morphological investigations indicate that the acceleration in the chiral polymer host is due to its longer Förster radius and improved compatibility with the dopants. Finally, multilayer CP PLEDs were fabricated and evaluated. Devices based on the chiral polymer host with the (R)- and (S)-dopants exhibit electroluminescence dissymmetry factors (g_EL) of 1.09 × 10⁻⁴ and −1.02 × 10⁻⁴ at a wavelength of 540 nm, respectively. Although challenges remain in the development of polymer hosts for CP PLEDs, our research demonstrates that chiroptical performances can be amplified by using chiral polymer hosts.

Polymer electroluminescence devices producing circularly polarized luminescence (CP PLEDs) have valuable photonic applications.     

Miscibility and interactions of polystyrene/polyolefine and polystyrene/poly(n-alkyl methacrylate) mixtures in dilute xylene solutions

The miscibility and intermolecular interactions between polystyrene (PS) and poly(ethylene-co-propylene) (EPC), as well as between PS and long-chain poly(alkyl methacrylates) (PAMA), namely, poly(dodecyl methacrylate) (PDDMA) and poly(octadecyl methacrylate) (PODMA), in dilute xylene solutions at 30 °C were studied. Investigated polymers are widely used as rheology modifiers, i.e. viscosity index improvers and pour point depressants for lubricating mineral oils. The specific and reduced viscosities of two- and three-component polymer solutions as well as intrinsic viscosities and Huggins’ parameter values were determined as functions of the polymer mixture composition and overall polymer concentration. The reduced viscosity was found to be linearly dependent on the overall polymer concentration. The observed viscosities of polymer mixtures were intermediate to those of the mixture constituents; the values decrease in the order: EPC > PS > PAMA. The specific viscosities of all the polymer mixtures obtained as the experimental results and calculated applying the Catsiff-Hewett and Krigbaum-Wall theoretical equations were considered. Since all the polymer/polymer pairs showed the negative viscometric interaction parameter values (Δb₁₂ < 0), the PS/EPC and EPC/PAMA mixtures were found to be immiscible. The observed repulsive molecular interactions originate from the differences in polymer composition and molar masses. This conclusion was supported by calculations employing the group contribution approach of Coleman, Graf and Painter. The calculated values of interaction parameters for (co)polymer blends, Λ₁₂, were 5.47, 6.42 and 13.1 J cm⁻³ for PS/PDDMA, PS/PODMA and PS/EPC, respectively.     

Hierarchical mesostructures of biodegradable triblock copolymers via evaporation-induced self-assembly directed by alkali metal ions

Hierarchical mesostructures of poly(ε-caprolactone)-b-poly(ethylene oxide)-b-poly(ε-caprolactone) (PCL-PEO-PCL) triblock copolymers have been grown from evaporation-induced self-assembly directed by alkali metal ions. The self-assembly process began with a dilute homogeneous solution of the triblock copolymers in a mixture of tetrahydrofuran (THF) and water. THF preferentially evaporated under reduced pressure and induced the formation of amphiphilic polymer micelles. The spherical polymer micelles formed both in deionized water and NaOH aqueous solution. However, different mesostructures were discovered during the film depositing process for scanning electron microscopy observation. The polymer micelles were observed for the deposition sample in deionized water while sisal-like hierarchical mesostructures resulted from the film deposition of polymer micelles in NaOH aqueous solution. The sisal-like mesostructures and their formation process were observed through scanning electron microscopy, transmission electron microscopy, fluorescent microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Detailed study revealed that during evaporation-induced self-assembly of PCL-PEO-PCL amphiphilic triblock copolymer directed by alkali metal ions, the sodium ions and polymer micelles increasingly concentrated in NaOH aqueous solution and the solvent quality for the diblock progressively decreased, which resulted in the stronger coordination between alkali metal ions and PEO ligands in the block copolymer and PEO segment crystallization.     

Preparation of biodegradable and thermoresponsive enzyme–polymer conjugates with controllable bioactivity via RAFT polymerization

The preparation of biodegradable and thermoresponsive enzyme–polymer bioconjugates with controllable enzymatic activity via reversible addition−fragmentation chain transfer (RAFT) polymerization and amidation conjugation reaction is presented. A new 2-mercaptothiazoline ester functionalized RAFT agent with intra-disulfide linkage was synthesized and used as chain transfer agent (CTA) to generate a biocompatible homopolymer, poly(ethyleneglycol) acrylate (polyPEG-A) and a thermoresponsive copolymer of poly(ethyleneglycol) acrylate with di(ethyleneglycol)ethyl ether acrylate [poly(PEG-A-co-DEG-A)]. These biodegradable and thermoresponsive polymers were then conjugated to the surface of glucose oxidase (GOx) under mild condition to afford the biodegradable and thermoresponsive enzyme–polymer conjugates. Cleavage of the polymer chains from the GOx surface obviously recovered the enzymatic activity. The thermoresponsive test of GOx-poly(PEG-A-co-DEG-A) revealed that the bioconjugate exhibited regular enzymatic activity fluctuation upon the temperature change below or above the lower critical solution temperature (LCST). The as-prepared enzyme–polymer conjugates were also characterized using ¹H NMR, UV–vis spectroscopy, polyacrylamide gel electrophoresis (PAGE) and biocatalytic activity tests. These smart enzyme–polymer conjugates would envision promising applications in biotechnology and biomedicine.     

Fabrication of an ��-lipoic acid-eluting poly-(D,L-lactide-co-caprolactone) cuff for the inhibition of neointimal formation

The purpose of this study was to develop a novel polymer cuff for the local delivery of α-lipoic acid (ALA) to inhibit neointimal formation in vivo. The polymer cuff was fabricated by incorporating the ALA into poly-(_D,L-lactide-co-caprolactone) 40:60 (PLC), with or without methoxy polyethylene glycol (MethoxyPEG). The release kinetics of ALA and in vitro degradation by hydrolysis were analyzed by HPLC and field emission scanning electron microscopy (FE-SEM), respectively. In vivo evaluation of the effect of the ALA-containing polymer cuff was carried out using a rat femoral artery cuff injury model. At 24 h, 48% or 87% of the ALA was released from PCL cuffs with or without MethoxyPEG. FE-SEM results indicated that ALA was blended homogenously in the PLC with MethoxyPEG, whereas ALA was distributed on the surface of the PLC cuff without MethoxyPEG. The PLC cuff with MethoxyPEG showed prolonged and controlled release of ALA in PBS, in contrast to the PLC cuff without MethoxyPEG. Both ALA-containing polymer cuffs had a significant effect on the inhibition of neointimal formation in rat femoral artery. Novel ALA-containing polymer cuffs made of PLC were found to be biocompatible and effective in inhibiting neointimal formation in vivo. Polymer cuffs containing MethoxyPEG allowed the release of ALA for one additional week, and the rate of drug release from the PLC could be controlled by changing the composition of the polymer. These findings demonstrate that polymer cuffs may be an easy tool for the evaluation of anti-restenotic agents in animal models.     

Polymer types regulation strategy toward the synthesis of carbonized polymer dots with excitation-wavelength dependent or independent fluorescence

Three kinds of carbonized polymer dots (CPDs) synthesized via a one-pot process from o-phenylenediamine (OPD), m-phenylenediamine (MPD) and p-phenylenediamine (PPD) exhibit excitation-wavelength independent yellow, green and red emissions, respectively. In sharp contrast, two kinds of CPDs prepared via a hydrothermal process from citric acid (CA) and diethylenetriamine (DETA) exhibit obvious excitation-wavelength dependent emissions. Through the characterization and comparison of the two types of CPDs, it is concretely revealed that the polymer structure types during the formation of CPDs can effectively control the fluorescence excitation-wavelength independence/dependence. The homogeneous polymer structures contained in CPDs contribute to excitation-wavelength independence, whereas random copolymer structures contribute to excitation-wavelength dependence. These studies are of great significance for further understanding the polymer structures and designing unique optical properties of CPDs.     

Structure-property relationships for novel wholly aromatic polyamide-hydrazides containing various proportions of para-phenylene and meta-phenylene units: I. Synthesis and characterization

A series of novel wholly aromatic polyamide-hydrazides was synthesized by a low temperature solution polycondensation reaction of either 4-amino-3-hydroxybenzhydrazide or 3-amino-4-hydroxybenzhydrazide with an equimolar amount of either terephthaloyl chloride (TCl), isophthaloyl chloride (ICl), or mixtures of various molar ratios of TCl and ICl in anhydrous N,N-dimethylacetamide (DMAc) as a solvent. Polymer structures were identified by elemental analysis and infrared spectroscopy. All the polymers have the same structural formula except the way of linking phenylene units inside the polymer chain. The content of para- and meta-phenylene moieties was varied within this series so that the changes in the latter were 10 mol % from polymer to polymer, starting from an overall content of 0-100 mol %. The prepared polymers were characterized for their properties in order to acquire clear understanding of the influence exerted by controlled structural variations in these polymers upon some of important properties, such as solubility, intrinsic viscosity, moisture regain, mechanical properties and thermal as well as thermo-oxidative stability. The polymers were readily soluble in several organic polar solvents such as DMAc, N,N-dimethylformamide, dimethyl sulphoxide, N-methyl-2-pyrrolidone and hexamethyl phosphoramide and could be cast into flexible films. Their solubilities were found to increase remarkably with introduction of meta-phenylene moieties into the polymer chains. Their intrinsic viscosities ranged from 0.73 to 4.83 dl g⁻¹ in DMAc at 30 °C and increased with the increase of para-phenylene units content. Mechanical properties of the films produced from these polymers are improved markedly by substitution of para-phenylene units for meta-phenylene units. Thermogravimetric studies revealed that the completely para-oriented type of polymer has better thermal and thermo-oxidative stability relative to that of the other polymers. Moreover, the results reveal that the prepared polymers have a great affinity to water sorption. The hydrophilic character increases as a function of meta-oriented phenylene rings incorporated into the polymer chains.     

In vitro and in vivo degradation behaviors of thermosensitive poly(organophosphazene) hydrogels

Biodegradable and thermosensitive poly(organophosphazenes) with various substituents were synthesized and their hydrolytic degradation properties were investigated in vitro and in vivo. The aqueous solutions of all polymers showed a sol-gel phase transition behavior depending on temperature changes. The side groups of polymers significantly affected the polymer degradation and accelerated hydrolysis of polymers in the order of carboxylic acid > depsipeptide > without carboxylic acid and depsipeptide. The increased gel strength led to the decreased hydrolysis rate. The polymer hydrogels with 750 Da of α-amino-ω-methoxy poly(ethylene glycol) were rapidly decreased by dissolution. The polymer degradation was also influenced by pH and temperature. The in vivo behaviors of mass decrease of the polymer hydrogels were similar with the in vitro results. These results suggest that the biodegradable and thermosensitive poly(organophosphazenes) hold great potentials as an injectable and biodegradable hydrogel for biomedical applications with controllable degradation rate.     

Dual-response nanocarrier based on graft copolymers with hydrazone bond linkages for improved drug delivery

Core–shell micelles with biodegradability, thermo- and pH-response were successfully demonstrated by poly(2-oxepane-1,5-dione-co-ɛ-caprolactone) (P(OPD-co-CL)) grafted with hydrophilic segments of amine-terminated poly(N-isopropylacrylamide) (At-PNIPAM). To compare with the graft copolymer, P(OPD-co-CL) block PNIPAM polymer was also prepared. The micelles with core–shell structure were formed with both graft and block copolymers by self-assembly in aqueous solutions, of which PNIPAM shell is thermo-response. Furthermore, P(OPD-co-CL)-g-PNIPAM also showed pH-sensitivity, which was attributed to the acid-cleavable property of the hydrazone bond. The low critical micelle concentrations (CMCs) of graft polymers and block polymers were 6.7 mg/L and 14.3 mg/L, respectively, which indicated the formation of stable micelles. Both drug-free and drug-loaded micelles were in uniformly spherical shape observed by transmission electron microscopy (TEM). The sizes of the drug-free and drug-loaded micelles prepared from graft polymer were 123.5 nm and 146.5 nm, respectively, and the sizes of those prepared from block polymer were 197.5 nm and 211.5 nm, respectively. The lower critical solution temperature (LCST) for the graft polymer was 34.3 °C, while that for the block polymer was 28.1 °C, demonstrating a thermo-response. The graft polymeric micelles exhibited thermo-triggered decelerated release at pH 7.4, and pH-triggered accelerated release at 25 °C in vitro release test, indicating that the graft polymeric micelles could be a promising site-specific drug delivery system for enhancing the bioavailability of the drug in targeted pathological areas.     

High-temperature solvent stability of sol–gel germania triblock polymer coatings in capillary microextraction on-line coupled to high-performance liquid chromatography

Germania-based sol–gel organic–inorganic hybrid coatings were prepared for on-line coupling of capillary microextraction with high-performance liquid chromatography. For this, a germania-based sol–gel precursor, tetra-n-butoxygermane and a hydroxy-terminated triblock copolymer, poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) were used. These sol–gel germania triblock polymer coatings were chemically anchored to the inner walls of a fused silica capillary (0.25 mm I.D.) in course of its evolution from the sol solution. Scanning electron microscopy images of the sol–gel germania triblock polymer coating were obtained to estimate the coating thickness. For the first time, the analyte distribution constants between a sol–gel germania organic–inorganic hybrid coating and the samples (K_cs) were determined. For a variety of analytes from different chemical classes, including polycyclic aromatic hydrocarbons (PAHs), ketones, alcohols, phenols and amines, the K_cs values ranged from 8.1 × 10¹ to 5.6 × 10⁴. Also, for the first time, the stability of the sol–gel germania-based coating in high-temperature reversed-phase solvent environment was evaluated. The sol–gel germania triblock polymer coatings were capable of surviving exposure to high-temperature solvent conditions (200 °C) with little change in extraction capabilities. This demonstrates that sol–gel germania triblock polymer hybrid materials might be suitable for further applications in high-temperature HPLC. The reproducibility of the method for preparation of the sol–gel germania triblock polymer coatings was also evaluated, and the capillary-to-capillary RSD values ranged from 5.3 to 6.5%. The use of higher flow rates in extraction was found to significantly reduce the time required (from 30–40 to 10–15 min) to reach equilibrium between the sol–gel germania triblock polymer coating and the analytes in the sample solution.     

Solvatochromic relationship: Prediction of distribution of ionic solutes in aqueous two-phase systems

Partition ratios of several ionic compounds in 20 different polymer/polymer aqueous two-phase systems (ATPS) containing 0.15 M NaCl in 0.01 M phosphate buffer, pH 7.4, were determined. The differences between the electrostatic properties of the phases in all the ATPS were estimated from partitioning of the homologous series of dinitrophenylated-amino acids. Also the solvatochromic solvent parameters characterizing the solvent dipolarity/polarizability (π*), solvent hydrogen-bond donor acidity (α), and solvent hydrogen-bond acceptor basicity (β) of aqueous media were measured in the coexisting phases of the ATPS. The solute-specific coefficients for the compounds examined were determined by the multiple linear regression analysis using the modified linear solvation energy relationship equation. The minimal number of ATPS necessary for determination of the coefficients was established and 10 ATPS were selected as a reference ATPS set. The solute-specific coefficients values obtained with this reference set of ATPS were used to predict the partition ratios for the compounds in 10 ATPS not included in the reference set. The predicted partition ratios values were compared to those determined experimentally and found to be in good agreement. It is concluded that the presented model of solute–solvent interactions as the driving force for solute partitioning in polymer/polymer ATPS describes experimental observations with 90–95% accuracy.     

Thermal analysis techniques for characterization of polymer materials

Routine DSC and TGA techniques, used to characterise polymer thermal stability, have been further used for assessment of comparative thermal stability of various polymer materials and for prediction of material lifetimes. The following materials were investigated: (1) commercial and experimental polymer materials - results for poly(vinyl chloride) (PVC) and bisphenol A polycarbonate (PC) are presented; (2) a polydimethylsiloxane-polytetrafluoroethylene (SIL-PTFE) coating system; and (3) commercially available linear low density polyethylene (PE-LLD), unmodified and modified chemically and physically. The plot of reciprocal temperature of initial decomposition 1/T_di vs log heating rate β has been recommended for assessment of comparative thermal stability. The lifetime of polymer materials was calculated from the plots of log time-to-failure, log t_f, vs reciprocal temperature 1/T, where t_f values were obtained using T_di from TGA measurements or directly from the oxidation induction time (OIT) data as criteria for initial deterioration of polymer thermal stability. The following sequences of increasing thermal stability were found for investigated materials:

(1)

PVC ? PC;

(2)

SIL < SIL-PTFE 20% < SIL-PTFE 50% ? PTFE;

(3)

(B) PE-LLD, grafted < (A) PE-LLD, unmodified < (C) PE-LLD, filled.

The lifetime of polymer materials predicted from the plots of log t_f vs 1/T are in reasonable agreement with experimental data and users' observations, e.g. approximately 1 year for PC and unmodified PE-LLD both at 373 K (100 °C) and for PVC at temperature of outdoor conditions about 298 K (25 °C).