Monomer-polymer System Research Articles

Ring-Opening Polymerization of a Bicyclic Lactone: Polyesters Derived from Norcamphor with Complete Chemical Recyclability.

Chemical recycling of polymers is an elegant approach to achieve a circular economy and address the sustainability and end-of-life issues of plastics. Herein, we report the ring-opening polymerization of a bicyclic lactone that is easily accessible from norcamphor. High molecular weight polyesters (Mn up to 164 kg mol-1) are obtained using ZnEt2 as catalyst, while the polymerizability of the monomer is good even at high temperatures. More importantly, the polymers can be completely depolymerized under thermolysis conditions to selectively recover the pristine monomer. Thus, the monomer design strategy of using ring-fused/hybridized lactones enables an innovative monomer-polymer system that shows both high polymerizability and high depolymerizability.

Ring-Opening Polymerization of Cyclic Phosphonates: Access to Inorganic Polymers with a PV–O Main Chain

We describe a new class of inorganic polymeric materials featuring a main chain consisting of PV-O bonds and aryl side groups, which was obtained with >70 repeat units by ring-opening polymerization of cyclic phosphonates. This monomer-polymer system was found to be dynamic in solution enabling selective depolymerization under dilute conditions, which can be tuned by varying the substituents. The polymers show high thermal stability to weight loss and can be easily fabricated into self-standing thin films. Structural characterizations of the cyclic 6- and 12-membered ring precursors are also described.

Influence of Thickness on the Holographic Parameters of H-PDLC Materials

For photopolymers the compound concentrations and final thickness of the sample should be known in order to model hologram formation and introduce the reaction-diffusion kinetics of the monomer-polymer system. In principle the cell thickness can be controlled by bead spacers between the two pieces of ITO glass. In this paper we report a study of the influence of thickness on the holographic properties of this type of materials. To fit the physical and optical thickness of the samples we used the rigorous coupled wave analysis assuming an exponential decay in the refractive index modulation.

A diffusion model of the development of concentration heterogeneities in a photopolymerizable environment with allowance for the limited compatibility of a monomer and a polymer

A diffusion model of the development of concentration heterogeneities of a photopolymerizable composite that takes into account the transition of the monomer-polymer system from the homophase state to the heterophase state with an increase in conversion is proposed. Numerical simulation shows that a significant increase in the amplitude of these heterogeneities is determined not only by the microsyneresis of the composite but also by the efficiency of their development in the homophase state at the initial stage of polymerization. The possibility of controlling the optical properties of the final polymeric material via initiation of the polymerization by radiation of different intensities in the regions of the homophase and heterophase states of the composite is discussed. The numerical-simulation results are experimentally verified.

Phenomenological model of anisotropic volume hologram formation in liquid-crystal-photopolymer mixtures

The real time formation of anisotropic volume holographic reflection gratings in a liquid-crystal/photopolymer mixture is studied. We develop a phenomenological model of grating formation that incorporates the photophysics and photochemistry of the initiator dye, reaction-diffusion kinetics of the monomer-polymer system, phase separation of the liquid crystal, nematic order evolution of liquid-crystal droplets, and volume shrinkage of the polymer. We then test this model by experimentally monitoring the diffraction efficiency for s and p polarization, Bragg wavelength, and laser scattering in real time as the grating is formed. The model yields good agreement with experimental data for different recording intensities and exposure times. We discuss the physics of the system as it evolves in time and explain the major features of anisotropic grating formation in acrylate-based holographic polymer-dispersed liquid crystals.

Local Properties in Disordered Mixed M1-xPxMonomer Polymer Crystal : A D-NMR Study

Abstract The influence of the polymerization on the structural phase transition in a mixed monomer-polymer pTS-D system is studied by D-NMR. Results are compared with previous neutron and Raman scattering results.

Interactions of poly-N6-methyladenylic acid and N6-substituted-9-methyladenines with poly-5-bromouridylic acid: a novel base-pairing.

The interaction of poly-N6-methyladenylic acid (poly(m6A) with poly-5-bromouridylic acid (poly(BU) was studied by the mixing curve method. A.1 m6A: 2 BU stoichiometry was clearly indicated over a wide range of ionic strengths at neutral pH, while the binding of poly(m6A) to poly(U) is known to occur with 1 m6A:1 U. Digestion by nuclease S1 confirmed this stoichiometry, indicating the absence of single strands in a 1:2 mixture. Heating profile analysis and hydroxyapatite column chromatography provided further confirmation of this finding. To determine whether 1:2 stoichiometry holds in a monomer-polymer system, the interaction of N6-methyl-9-methyladenine (m6m9A), a corresponding monomer of poly(m6A), with poly(BU) was investigated. Equilibrium dialysis experiments showed the stoichiometry of the interaction to be 1 m6A:2 BU. Thus, we would describe some structural studies of the above complexes using c.d. and i.r. spectroscopy. Poly (m6A).2poly(BU) and m6m9A.2poly(BU) are helical and analogous to each other in structure, and the bases in the complexes are all bound by hydrogen-bonding. N6-(delta 2-isopentenyl)- and N6-allyl-9-methyladenine were also found to form complexes with poly(BU), giving similar c.d. spectra with that of m6m9A.2poly(BU). The melting experiments indicated the Tms to be substantially decreased, compared to the parent unmodified complexes, even though the Tm dependence of the polymer complex on salt concentration conforms to the typical triple strand. In the following, the biological significance of this novel pairing will be discussed.

Polymérisation en milieu précipitant du styrène en solution dans différents alcools

Earlier studies from this laboratory on the polymerizations of acrylic acid and acrylonitrile under precipitating conditions have shown that the auto-acceleration is not caused by non-stationary conditions resulting from the precipitation of growing chains (“occlusion effect”) but by a “matrix effect”, an oriented association complex between the monomer and the polymer formed in the early stages of the reaction leading to assisted propagation. In the present work, a non-polar monomer-polymer system was selected in which molecular associations are unlikely. It was found that when polystyrene precipitates as a fine powder (in diluted monomer solutions in alcohols) auto-acceleration is observed but its extent drops with increasing rate of initiation and increasing temperature. Such situations do not arise in polymerizing systems in which a “matrix effect” operates. The study of the post-polymerization and of the swelling of polystyrene in styrene (10-propanol (90) mixtures) led to the conclusion that polystyrene in equilibrium with this mixture exhibits a glass transition temperature at ca 50°. The various results obtained in this study conform with the assumption of an occlusion effect. The growing chains being buried in the precipitated polymer, chain termination is severely restricted and becomes the determining step in the polymerization.

The variation in molecular mobility during crosslinking of oligoester acrylates

The kinetics of three dimensional polymerization of α,ω- bis-(methacrylyloxyethylenoxycarbonyloxy)-1,3-propylene monomer and the nature of the change in molecular mobility in the course of formation of highly crosslinked polymer, have been investigated by the broad line and pulsed NMR methods. It is shown that when formation of a three dimensional network begins during polymerization of this monomer, a broad component of the NMR line appears, corresponding to protons of low mobility, belonging to the polymethacrylate chain being formed. Quantitative characteristics of the monomer-polymer system have been obtained by separation of the two component, resonance absorption spectra into the narrow and broad components. In study of the polymerization kinetics of the above monomer, all other conditions being the same, the results of the two NMR methods are in agreement.

Structuro-physical changes during radical polymerization

The formation of linear and crosslinked polymers has been investigated by spectroturbidimetry and microscopy. It is shown that during the course of polymerization the monomer-polymer system undergoes a complex structural evolution, passing in the general case through the stages of molecular solution, of dispersion of polymer particles in monomer and of a micro-heterogeneous polymeric body. These consecutive changes are responsible for such characteristic features of the kinetics of radical polymerization as autoacceleration and autoretardation. Change in the conditions and kinetics of polymerization in turn affect the process of structure formation and the structure of the solid polymer formed.

Diffusion of Residual Monomer in Polymer Resins

A simplified mathematical model which made use of Fick's laws of diffusion written in spherical coordinates was developed to describe the rate of diffusion of residual monomers from polymer resins. The properties of the monomer-polymer system which influenced the amount of monomer remaining in the polymer as a function of time were the diffusivity and solubility of the monomer in the polymer, and the particle size of the polymer resin. This model was used to analyze literature data on the diffusion of residual vinyl chloride monomer in polyvinyl chloride resins made by the suspension process. It was concluded that particle size of the resin was a significant parameter which should be taken advantage of in process equipment designed to remove residual monomer from PVC resins. The diffusivity of the monomer in the polymer was a function of the solubility of the monomer in the polymer. Monomer solubility can be determined from Henry's law. It was suggested that this model could be adapted to describe diffusion of monomers from any monomer-polymer system, and would be a useful approach to modeling the transport of nonreactive chemical additives from plastics.

Diffusion of residual monomer in polymer resins.

A simplified mathematical model which made use of Fick's laws of diffusion written in spherical coordinates was developed to describe the rate of diffusion of residual monomers from polymer resins. The properties of the monomer-polymer system which influenced the amount of monomer remaining in the polymer as a function of time were the diffusivity and solubility of the monomer in the polymer, and the particle size of the polymer resin. This model was used to analyze literature data on the diffusion of residual vinyl chloride monomer in polyvinyl chloride resins made by the suspension process. It was concluded that particle size of the resin was a significant parameter which should be taken advantage of in process equipment designed to remove residual monomer from PVC resins. The diffusivity of the monomer in the polymer was a function of the solubility of the monomer in the polymer. Monomer solubility can be determined from Henry's law. It was suggested that this model could be adapted to describe diffusion of monomers from any monomer-polymer system, and would be a useful approach to modeling the transport of nonreactive chemical additives from plastics.

Molecular mobility and the kinetics of radical polymerization

A “dielecometer-calorimeter” apparatus has been constructed that enables the heat evolution, dielectric permeability, ϵ′, and the conductivity, σ, of a monomer-polymer system to be recorded simultaneously during polymerization. The radical polymerization of a number of acrylates, methacrylates and dimethacrylate oligomers has been studied. A correlation has been established between the specific molecular mobility in the monomer-polymer system, at polymerization to various extents, with the kinetic characteristics of the process.

Investigations in the field of solid-state polymerizations—XXXIII: Molecular motion studies on acenaphthylene-poly-(acenaphthylene) systems

Spin-lattice relaxation measurements of composite systems with different monomer-to polymer ratios are consistent with the phase diagram described previously. Relaxation curve of the system with monomer content higher than M cr shows behaviour different from those for systems of higher polymer content. Below M cr, all composites have the same slope and similar T 1 values in the glassy state. Infra-red spectra confirm the similarity between the molecular arrangement in the monomerpolymer system and in the crystalline monomer. X-Ray diffraction measurements show a diffusion of monomer molecules from their crystalline particles into the glassy polymer. According to the new diffusion scheme proposed, an interface layer (δ) is formed between the crystalline monomer and the glassy polymer in which a diffusion, controlled polymerization can proceed.

The Growth of Polystyrene Latex Particles

Abstract Our understanding of the factors controlling the growth of polystyrene latex particles has recently undergone extensive revision. For this compatible monomer-polymer system, it was generally presumed that monomer and polymer were uniformly distributed throughout the particles, whereas we have found quite the contrary. Under a wide range of conditions, growing latex particles actually exhibit a distributed structure in which a monomer-rich shell encapsulates a polymer-rich core. First elucidated in kinetic studies of styrene emulsion polymerization, this behavior has also been observed in particles which reside in a state of equilibrium saturation with monomer. The encapsulation phenomenon is governed by the microscopic thermodynamic environment of the latex particles which has, in turn, a profound effect upon the conformational behavior of the long-chain polymer molecules as they interact with the particle-water interface. The control of latex particle properties by the staged addition of several...

Transhydrogenation in the human placenta.

ABSTRACT Human placental 17β-oestradiol dehydrogenase exists in two electrophoretic forms which are either isozymes or components of a monomerpolymer system. Both forms utilize NAD+ and NADP+ as cofactor and 17β-oestradiol-3-sulfate and testosterone as substrate. Using a method developed to detect transhydrogenase activity on starch gel after electrophoresis, both forms were shown to mediate transhydrogenation but transhydrogenase:dehydrogenase activity ratios of the two forms were different. No oestrogen-sensitive transhydrogenase distinct from 17β-oestradiol dehydrogenase was observed on electrophoresis of placental crude supernatant and purified preparations at several pH values.

The solubility and swelling of latex particles

A vapor pressure method has been used to determine the solubility of vinyl acetate, styrene, and vinyl hexanoate in both the aqueous phase and in the polymer particles. All the systems have been measured at 30° or 60°C. or both. The vapor pressure measurement permits an estimation of the partial molar free energy of the monomer-polymer system. A thermodynamic treatment of the latex system, modified from that of Morton, yields a relationship from which the monomer-polymer interaction parameter, μ, and the interfacial tension, γ, may be obtained. Several tests of the thermodynamic relationship involving variations of the interfacial tension proved successful. Reasonable values are obtained for both the interaction parameter and the interfacial tension, although checks of two interaction parameters with literature values show some differences due to dissimilarities in the conditions of measurement. The solubility figures for the systems studied are high compared to most literature values at other temperatures; however, the difference is readily explained by consideration of the dependence of solubility on the temperature. Increased solvency of the monomers at polymerization temperatures tends to swell the particles more than at ambient temperatures. The increased solubility of monomer in the polymer is reflected in a lowering of the interaction parameter. The values determined at polymerization temperatures are obviously more representative of the polymerizing system.

The free-radical polymerization of ethylene—III. Polymerization of ethylene in a heterogeneous monomer-polymer system

The free-radical polymerization of ethylene—III. Polymerization of ethylene in a heterogeneous monomer-polymer system

Free radical polymerization of ethylene—III. Polymerization of ethylene under conditions of heterogeneity of the monomer-polymer system: S. G. Lyubetskii, B. A. Dolgoplosk and B. L. Erusalimskii, Vysokomol. soedin. 4: No. 4, 533–539, 1962

Free radical polymerization of ethylene—III. Polymerization of ethylene under conditions of heterogeneity of the monomer-polymer system: S. G. Lyubetskii, B. A. Dolgoplosk and B. L. Erusalimskii, Vysokomol. soedin. 4: No. 4, 533–539, 1962

Hydrogen Fluoride Polymer Spectrum, Hexamer and Tetramer

The experimental techniques employed to investigate the polymer absorption are presented. Experimental results at various pressures at temperatures from —70°C to +73°C are presented. The more important qualitative features noted are: (1) the absorption is strongly dependent upon both the temperature and pressure; (2) in some cases the shape of the bands is dependent upon the pressure; (3) at low temperature only very low pressures of vapor (hence of polymer) are necessary to observe some absorption. The application of Dalton's law, the law of mass action, Lambert's law, and Beer's law, as well as Van't Hoff's equation to the hydrogen fluoride monomer-polymer system is discussed. It is then shown that under some special circumstances the absorption varies simply as the fourth power of the pressure, under others as the sixth power of the pressure, but more generally where the absorption is strong as the sum of two terms, one containing the fourth power of the pressure the other the sixth power. The absorption thus corresponds to the overlapping spectra of a tetramer and of a hexamer, which can be separated on the basis of this pressure dependence. From the temperature variation of the absorption, the heats of polymerization are estimated as ΔH4 = —19 kcal/mole and ΔH6 = —40 kcal/mole. In general, the absorption outside the range of monomer absorption is as consistent with a tetramer-hexamer interpretation for deuterium fluoride as for hydrogen fluoride.