Anomalous viscosity behavior of some poly(methyl methacrylate)s prepared by anionic polymerization

A series of poly(methyl methacrylate)s with molecular weights in the range 3.0 × 10⁴–1.03 × 10⁶ have been prepared by anionic polymerization and their limiting viscosity numbers determined in a variety of solvents. It was found that whereas the higher-molecular-weight polymers behaved normally, the lower-molecular-weight polymers showed anomalous behavior. First, the limiting viscosity numbers of the lower-molecular-weight polymers were much higher than expected, and, second, their number-average molecular weights as measured by gel permeation chromatography were considerably smaller than those determined by membrane osmometry.     

The influence of molecular interaction on polymerization—11: A study of the influence of the solvent on the tacticities of poly(2-naphthyl methacrylated) and poly(cumylphenyl methacrylate) obtained in various solvents

Polymerizations of 2-naphthyl methacrylate and 4(1-methylphenethyl)phenyl methacrylate (cumylphenyl methacrylate) have been carried out in solvents with different dielectric constants and donor numbers (DN). By means of ¹H-NMR and fluorescence spectroscopy, the tacticities of the polymers were studied. It was found that the structures of the polymers depend on the dielectric constant of the solvent and not on its donor number. In solvents with high dielectric constant, the contents of isotactic triads are higher than for solvents with low dielectric constants.     

Synthesis of Phenacylmethacrylate: Its Characterization and Polymerization

Abstract

Phenacylmethacrylate (PAMA), a new monomer containing two carbonyl groups (C[dbnd]O), was obtained from phenacyl chloride and sodium methacrylate. The homopolymer of PAMA and its copolymer with styrene were prepared in dioxane by using benzoylperoxide (Bz₂O₂) as initiator. IR, ¹H-NMR and ¹³C-NMR techniques were used to identify the structure of the monomer and polymers. The density of monomer, homopolymer and copolymer were found to be 1.13; 1.35 and 1.10 gr/ml respectively. Also, limit viscosity numbers, solubility parameters, glass transition and decomposition temperatures of polymers were determined.     

Poly(methylene sebacate): Synthesis and characterization

The synthesis of poly(methylene sebacate) was carried out via the reaction of cesium sebacate with bromochloromethane in N-methylpyrrolidone over a range of temperatures (55–130°C). A number of polymers having limiting viscosity numbers in the range of 0.29–0.94 dL g^?1 (CHCl₃; 25°C) were characterized by elemental analyses, ¹H- and ¹³C-NMR, DSC, and GPC techniques. The polymerization was found to be very rapid at 100°C, being complete in ca. 15 min. and was relatively insensitive to the stoichiometric ratio of the monomers. As high molecular weight polymers were produced without the quantitative conversion of the reactants, the polymerization is considered to be occurring by an interfacial mechanism.     

Studies on the odd‐even effect of methylene spacers in poly(pyromellitimide‐ester)s

Three series of poly(pyromellitimide‐ester)s were synthesized from various N,N′‐bis(ω‐hydroxyalkyl)pyromellitimides (HAPMIs) by melt condensation with dicarboxylic acids, including terephthalic acid (TPA), 4,4′‐biphenyldicarboxylic acid (BPDA), and 4,4′‐azobenzenedicarboxylic acid (ABDA). Polymers were characterized by elemental analysis, solubility, inherent viscosity, spectra (IR, ¹H‐NMR, ¹³C‐NMR), and X‐ray diffraction (XRD). Thermal stability and phase transition behaviour were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and hot‐stage optical polarized microscopy (HOPM). The d‐spacings, calculated from XRD data, showed an odd‐even effect with varying numbers of methylene spacers. Crystallinity of polymers decreased in the following order: azobenzene > biphenyl > phenyl polymers. Similarly, DSC‐obtained melting temperatures (T_m's) showed an odd‐even effect, and glass transition temperatures (T_g's) decreased with increasing numbers of methylene spacers. Thermal stability decreased as methylene chain length increased. Thermal stability of polymers occurred in the following order: phenyl > biphenyl > azobenzene polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1755–1761, 1999     

Structure Control in Sol-Gel Silica Synthesis Using Ionene Polymers. 2: Evidence from Spectroscopic Analysis

By use of the Menshutkin reaction a variety of polyviologens have been synthesised containing bromide or tosylate counter-ions and varying numbers of methylene units. These ionene polymers have been shown to display lyotropic liquid crystalline behaviour. The effects of these polyviologens on the structure of growing silica networks synthesised using the sol-gel method were studied by spectroscopic analysis. Depending on the concentration, the type of polyviologen and whether a lyotropic liquid crystalline phase was used, evidence for an effect of these polymers on silica structure was observed using FTIR and ¹H NMR spectroscopies. The presence and strength of an absorption band at 550 cm^–1 (coupled with an absorption at 450 cm^–1) was suggestive of some ordering occurring in these materials. Additionally, possible evidence of specific interactions involving the water molecules was obtained from ¹H NMR spectroscopy.     

Effects of adsorbed polyelectrolytes on convective flow and diffusion in porous membranes

Poly(acrylic acid) and poly(styrene sulfonate) were adsorbed from aqueous solutions to track-etched mica membranes with pores of radius 290 to 1400 Å. Effects of the adsorbed polymers on momentum and mass transport within the pores were studied by measuring the decrease in both the hydraulic and diffusional permeabilities caused by the presence of the polymers. The diffusional permeability was determined by measuring the flux of a small, uncharged solute molecule (thiourea). Polymer-free, aqueous solutions of potassium chloride (KCl) were used in all transport experiments. The reduction in hydraulic permeability increased with a decrease in KCl concentration in the range 10^-2 to 10^-1 molarity (M), but was independent of electrolyte concentration below 10^-2 M, presumably because the small pores constrained expansion of the adsorbed polymer chains. Shear thickening effects, that is, a decrease in hydraulic permeability with increasing solvent velocity through the pores, was observed with both polymers at 10^-1 M KCl in pores of 600 Å or smaller. Effects of the polymer on diffusional permeability of thiourea, on the other hand, were relatively insensitive to electrolyte concentration. Perhaps the most significant result is that the reduction in diffusional permeability was substantially less than the reduction in hydraulic permeability at each pore size and electrolyte concentration, indicating that the blockage of momentum transport by these adsorbed polymers is greater than the blockage of diffusion of a small solute. Measurements of thiourea transport by simultaneous diffusion and convection over a range in Peclet numbers from -2 to +2 showed that thiourea was filtered by the polymer. This filtration was probably not due to steric limitations on the thiourea, rather it is likely that thiourea was excluded from the water which solvated densely packed regions of the polymer chains.     

Synthesis and Characterization of Amphiphilic PEG Based Aliphatic and Aromatic Polymers and their Self-Assembling Behavior

Twelve amphiphilic polymers were synthesized using poly(ethylene glycols) (PEGs) of different molecular weights, viz. 1000, 2000 and 4000 as hydrophilic block and linkers namely azelaic acid, sebacic acid, dimethyl isophthalate acid and dimethyl terephthalate as hydrophobic block in the presence of catalyst Conc. H₂SO₄. Synthesized polymers were characterized by using ¹H-NMR, ¹³C-NMR and IR spectroscopy. Micellar sizes of the polymers were determined using Dynamic Light Scattering (DLS) which ranged from 51.6–174 nm for aliphatic polymers and 135.5–371 nm for aromatic polymers. Transmission Electron Microscope (TEM) results confirm the findings of DLS. Critical Micelle Concentrations (CMC) of the synthesized polymers were determined using electrical conductivity meter which ranged from 95 to 130 mg L^?1 for aliphatic polymers and 420–1500 mg L^?1 for aromatic polymers.     

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.     

Luminescent polymers with discrete emitter units

Optical absorption and photo-luminescence measurements were performed on a series of semiconducting polymers, based upon phenylene linkages, that have discrete emitter units. In these polymers, broken conjugation has been achieved in two ways: by introducing metalinkages between various numbers of para-connected aromatic groups or by severe steric distortion of a fully conjugated main chain. In either case, electronic states are localized on relatively small units, resulting in a large (π, π^*) band gap. The band gap decreases with increasing emitter unit conjugation, as expected. Blue light emission was observed from these materials, with the peak emission wavelength red shifted (by greater than 1 eV on average) from the peak absorption. © 1994 John Wiley & Sons, Inc.     

Synthesis of Chiral Sulfur‐Containing Polymers: Asymmetric Copolymerization of meso‐Epoxides and Carbonyl Sulfide

Synthesis of chiral sulfur‐containing polymers was realized for the first time by the asymmetric alternating copolymerization of achiral meso‐epoxides with carbonyl sulfide (COS) using catalyst systems based on enantiopure binaphthol‐linked dinuclear Co^III complexes under mild reaction conditions. The resultant poly(monothiocarbonate)s have main‐chain chirality and more than 99 % isotacticity. Notably, the stereoregular copolymers are typical semicrystalline thermoplastics with high melting temperatures up to 232 °C. Additionally, these sulfur‐containing polymers have good optical properties with refractive indices of up to 1.56 and Abbe's numbers of up to 43.     

Synthesis of third‐order non‐linear optical polymers based on conjugated poly(heteroarylene methines)

A series of 10 new poly(heteroarylene methylenes) containing one pyrrole or thiophene ring alternating with a carbon atom in the main chain were synthesized and characterized. The polymers which were synthesized in the air were found to be partially dehydrogenated by the oxygen, that is, the bridge carbon atoms between pyrrole or thiophene rings were partially sp³ atoms and partially sp² atoms. However the polymers which were synthesized in the flowing nitrogen atmosphere were found to be deoxidized, that is the bridge atoms were sp³ atoms. The deoxidized polymers could be oxidatively dehydrogenated with tetrchlorobenzoquinone. These polymers are useful model systems to investigate the effect of conjugation length on the electronic and optical properties of conjugated polymers. Third‐order optical non‐linearities of the reulting polymers were studied by z‐scan techniques. The results show that the reulting polymers exhibited large third‐order optical non‐linear susceptibilities as large as 10^?8 esu. Copyright © 2004 John Wiley & Sons, Ltd.     

Ionic conductivity of multiarm star polymer/LiClO4 electrolytes

A series of polymer electrolytes based on multiarm polymers and lithium salt complexes were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and impedance measurement. The relationships of conductivity with salt concentration, temperature, and arm numbers are discussed. It is suggested that the star polymer has a higher solvency and ion transfer ability on lithium salts than on linear polymers. The conductivity maximum appeared at a higher salt concentration ([EO]/[Li] = 4). Impedance measurement suggested that the optimum conductivity was 2 × 10^?4 s · cm^?1. The conductivity increased with temperature and the dependence of ionic conductivity on temperature fits the Arrhenius equation. Among the studied systems, the star polymer with a five arm number performs better than other structures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4195–4198, 2004     

Hooke numbers of polymers

Hooke numbers He ≡ σ_b/(E) are calculated from published ultimate tensile strengths σ_b, tensile moduli E, and ultimate elongations ?_b. Data for common thermoplastics and natural fibers each follow a function He = [1 + (?_b/?_crit)^ab]^?1/b with a Hookean region I (He = 1) at ?_b ? ?_crit, a non-Hookean region III at ?_b ? _crit, and a transition region II for ?_b ≈ ?_crit. Only non-Hookean regions III were found for semisimultaneous interpenetrating networks from polyisobutylene-polymethyl methacrylate, thermoplastic elastomers from segmented polyamide-polyethers, molecular composites from poly(p-phenylene benzobisthiazole) and poly[2,5(6)-benzimidazole], and three groups of various synthetic fibers. The Hooke numbers of lyotropic and thermotropic liquid-crystalline polymers vary with the heat treatment and depend on orientation angles for orientation angles greater than ca. 10°. Hooke numbers much greater than 1 are observed for highly stressed polymers. ©1995 John Wiley & Sons, Inc.     

Nanoporous materials based on spiroketal and spirothioketal polymers for separating methanol-toluene mixture

Organic microporous materials based on spiroketal and spirothioketal polymers were synthesized through 1,3-dioxol-forming polymerization reaction between pentaerythritol or pentaerythritol tetrathiol and different types of cyclohexa-1,4-dione derivatives. The structure of the prepared polymers was confirmed by NMR spectroscopy and molecular mass measurements. Nitrogen adsorption/desorption isotherms of the prepared polymers show a large amount of nitrogen adsorbed at low relative pressure indicating microporosity. These polymers have Brunauer Emmitt and Teller (BET) surface areas in the range from 492 (m² g⁻¹) to 685 (m² g⁻¹). The prepared polymers were found to be useful for pervaporation separation of methanol-toluene mixture with a separation factor up to 12.5 and fluxes, varying between 6.7 × 10⁻³ kg/(m² h) and 13.4 × 10⁻³ kg/(m² h).     

Synthesis and characterization of novel 1,3,4-oxadiazole- or 1,3,4-thiadiazole-containing wholly conjugated polyazomethines

A series of thermally stable and semiconducting polyazomethines containing 1,3,4-oxadiazole or 1,3,4-thiadiazole ring in the polymer backbone were synthesized by the simple solution poly-condensation of dialdehydes with the preformed nuclei with aromatic diamines under mild conditions. To elucidate the structure and also structure-property relationships of the polymers, model compounds were prepared under the same reaction conditions. These polyazomethines having a wholly conjugated system were yellow powders and had reduced viscosities up to 0.38 dL/g in concentrated sulfuric acid and electric conductivity as high as 10^?11 S cm^?1 at room temperature. Thermogravimetry showed that all the polymers were heat resistant up to around 400°C, in both air and nitrogen atmospheres. Their completely black colored charge-transfer complexes were prepared by iodine-doping of the polymers. The room temperature conductivity of the polymers was found to be markedly increased up to the orders of 10^?6–10^?7 S cm^?1 upon doping. The highest value attained was 4.8 x 10^?6 S cm^?1. Comparison of electronic spectra of the polymers with those of the model compounds indicated the π-electrons in the polymers are extensively delocalized along the polymer main chain.     

A study of the surface analysis of some water‐soluble polymers by inverse gas chromatography

The surface characterization of 2‐(dimethylamino)ethylmethacrylate (DMA) and 2‐(N‐morpholino)ethylmethacrylate (MEMA) homopolymers and DMA–MEMA diblock copolymer was studied using inverse‐gas chromatography (IGC). The analyzed surface properties of (co)polymers were the dispersive component of the surface energy ( ) and the acid–base characters of (co)polymer surfaces. The specific free energy (ΔG^sp), enthalpy (ΔH^sp), and entropy (ΔS^sp) of adsorption of polar probes on (co)polymers were calculated. The values of ΔH^sp were correlated with both the donor and the modified acceptor numbers (AN) of the probes to quantify the acidic K_A and the basic K_D parameters of (co)polymer surfaces. The values obtained for the K_A and K_D parameters indicated basic characters for the surface of (co)polymers. The dispersive component values of the surface energy and the acid–base surface parameters of the DMA–MEMA diblock copolymer surface were found to be between those homopolymers as expected. Copyright © 2008 John Wiley & Sons, Ltd.     

Molecular structure parameters in certain semiconducting polymers

The condensation polymers formed by condensing aromatic hydrocarbons or their derivatives with aromatic acids are quite conductive. The room temperature resistivities of 42 polymers studied here range from 10² to 10¹² ohm-cm. It is found that the resistivities are inversely related to the number of fused rings in the hydrocarbon portion of the monomer for either the homopolymers or copolymers. The resistivities are strongly dependent, inversely, upon the acid strength of the acid monomer reactants. For all the polymers studied, the conductivity σ depended upon the pressure P as ln(σ/σ₀) = (b^*/k)P^1/2 where b^* is seen to be an inverse function of the number of fused rings in the monomer in accord with theory. The resistivity ρ varied with absolute temperature T, as ln ρ ∞ (1/T) for all polymers. Thermoelectric powers were determined, and the various relationships established among energy interval, resistivity at “infinite temperature,” carrier concentrations and mobility ratios, number of fused rings, and pressure coefficients are discussed. The polymers are p-type. Doping by Be⁺⁺ or Cu⁺⁺ has a small effect, increasing the conductivity slightly. Electron spin concentrations and carrier concentrations are directly related among the polymers, being found nearly equal for the most conductive but differing by up to nine orders of magnitude in the least conductive polymers.     

Cation binding properties of crown ether-modified polyethylenimines

Crown ether-modified polyethylenimines (PEI-CR) were prepared to elucidate their cation binding efficiency and selectivity by liquid-liquid and solid-liquid extraction methods. With alkali metal cations it was found that polyethylenimines containing benzo-15-crown-5 moieties (Ia and Ib) extracted all cations examined more efficiently than their monomeric analogs, especially in the cases of K⁺ and Rb⁺ cations. The solid-liquid extraction revealed clearly that the polymers complexed with K⁺ and Rb⁺ cations according to a 1:2 cation-to-crown stoichiometry. The high selectivities of the polymers for K⁺ and Rb⁺ were interpreted in terms of the favourable conformation of the polymer chain for the formation of intramolecular 1:2 complexes. On the contrary, these polymers bound alkali earth cations less effectively with low selectivities.     

Functional monomers and polymers. CXXI. Methylation and interaction studies on adenine containing polymethacrylate derivatives

Studies of the methylation of polymethacrylate derivatives with adenine bases were made in comparison to those with uracil bases. The polymethacrylate derivatives with adenine bases were methylated by using methyl iodide in dimethyl sulfoxide solution to produce polymers that contained N¹-methyladenine and N¹, N⁶-dimethyladenine units. The products were identified by spectroscopic data and by preparing their model compounds. The methylated polymers obtained were further applied in a study of polymer complex formation with uracil-base polymers.