Chain Macromolecules Research Articles

Polymerization of vinylene carbonate as well as aminolysis and hydrolysis of poly(vinylene carbonate)

Poly(vinylene carbonate) was prepared via both bulk and solution polymerization. The products of bulk polymerization were mainly crosslinked, which was due to transfer reactions between the chain radicals and macromolecules. In solution polymerization, only soluble and low-molecular-weight polymers could be obtained because of chain transfer reactions with the solvents, and the transfer constant of N, N-dimethylformamide in the polymerization of vinylene carbonate at 60°C, C S=0.0228, was determined. Additionally, aminolysis and hydrolysis of poly(vinylene carbonate) and its model compound – ethylene carbonate were studied, respectively.

Fluorescence property on solutions of zwitterionic surfactant tetradecylbetaine in the presence of macromolecules

The fluorescence property of zwitterionic surfactant tetradecylbetaine (C 14BE) solutions in the presence of polyvinylpyrrolidone (PVPk30 and PVPk90), or Xanthan (Xc) have been investigated by steady-state fluorescence probe. The intensity ratio of the first and third peaks ( I 1/ I 3) of the monomer and that of the excimer to monomer ( I e/ I m), and the aggregation number of the aggregates have been monitored. The results showed that C 14BE/PVP and C 14BE/Xc interactions mostly occur at the micelle surface. The C 14BE clusters or micelles are bound to macromolecule chains by electrostatic force for PVP and by hydrogen-bonding for Xc, respectively.

Conformational statistics of macromolecules using generalized convolution

A new technique for generating statistical properties of chain-molecule conformations is presented. Conditional probability density functions (PDFs) describing the frequency of occurrence of the relative position and orientation of frames of reference affixed to selected backbone atoms serve as the inputs. Ensemble statistical properties of whole chains are generated by performing multiple generalized convolutions of these conditional PDFs. The formulation is shown to include classical theories such as the hindered and freely rotating chains, the Gaussian random walk, and the rotational isomeric state model. The convolution model is modified to include the long-range effects of excluded volume. An analytical example is used to illustrate the procedure. A general algorithm to calculate the ensemble properties of an arbitrary chain macromolecule is presented. In this algorithm, each of the N degrees of freedom (e.g. torsion angles) is assumed to have K discrete states. Using the convolution procedure, a chain is divided into P statistical units. The computational requirement is reduced from an O(KN) calculation (corresponding to direct enumeration) to one which is O(P(C+KN/P)) where C is the computational complexity of the convolution procedure. In the case of a homopolymer, computations are reduced further to O(Clog(P)+KN/P).

Preparation of electrically conducting polypyrrole in oil/water microemulsion

Nanoscopic conducting polypyrrole powder was prepared in an oil/water microemulsion with FeCl3 as a dopant. Compared with solution and conventional emulsion polymerizations, a microemulsion polymerization system increases the yield of the resultant polypyrrole. The results of FTIR spectra and thermal analysis studies indicate that the microemulsion polymerization system increased the extent of the π-conjugation length along the polymer backbone and ordered the arrangement of the macromolecule chains. These two effects bring about enhanced conductivity as well as higher thermal stability of polypyrrole. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 135–140, 2000

Predicting the rapid devolatilization of diverse forms of biomass with bio-flashchain

This paper introduces a new reaction model for the rapid devolatilization of diverse forms of biomass called bio-FLASHCHAIN (bio-FC). Given the proximate and ultimate analyses and the thermal history and pressure, bio-FC predicts the complete distribution of primary devolatilization products from paper and any form of wood, grass, and agricultural residue, including the yields of tar and all major gas species, the elemental compositions of tars and chars, and the molecular weight distribution of tar. Biomass is represented as a chain copolymer of cellulose and a lignin-like component. The actual composition and structure of cellulose are implemented, whereas the composition of the lignin-like component is assigned from the ultimate analysis of the whole biomass. The reaction scheme is based on the depolymerization of a mixture of chain macromolecules into fragments that volatilize into tar, partially decompose into gases, or recombine with the nascent char matrix. Comparisons to measurements demonstrate that bio-FC is a macromolecular reaction framework that can represent the complete distribution of primary devolatilization products from biomass. They also suggest that the model predictions will express the impact of variations in the most important operating conditions. The novel calibration procedure for the impact of mineral catalysis does not incorporate detailed mineralogical analyses or measured product yields. But many more evaluations are necessary to establish that it is suitable for the complete range of biomass fuel properties.

Temperature effects in hydrodynamic properties of comb-like polymer with laterally attached mesogenic units

The specific temperature effects in hydrodynamic properties (intrinsic viscosity, sedimentation velocity and translational diffusion) of side-on comb-like polymers with molecular weights from 5.70×10 5 to 3.02×10 6 were observed in dilute solution in two different solvents, benzene and chloroform, over a temperature range from 2 to 73°C. The viscosity temperature coefficient dln[ η]/d T was found to be negative in sign in chloroform (−0.007 K −1) and positive in benzene (+0.005 K −1). Increase in temperature leads to intensification of the excluded volume effects in real benzene solution of the polymer and to weakening of those in chloroform. Simultaneously, increase in temperature leads to decreasing unperturbed dimensions of the macromolecule chain in both the solvents. This effect is more pronounced in benzene (dln〈 h 2〉/d T=−0.005 K −1, where 〈 h 2〉 is the mean-square end-to-end distance) than in chloroform (−0.001 K −1). Origins of the temperature effects are discussed with relation to the lateral structure of the macromolecule where every monomer unit contains the threecyclic mesogenic moiety which is laterally (with the middle part) attached to a side chain consisting of 11 carbon atoms.

Nuclear magnetic resonance study of commercial poly(vinyl acetate)

The commercial poly(vinyl acetate) bulk was studied by nuclear magnetic resonance (NMR) at solution and solid state to understand much better the behavior of this polymer to obtain information on structure, sample molecular mobility, and heterogeneity. To analyze the behavior of this polymer, we have chosen NMR techniques, such as carbon-13 solution, magic angle spinning, cross-polarization/magic angle spinning, proton spin-relaxation time in the rotating frame parameter (T1ρ), and dipolar dephasing experiment. Therefore, from the NMR response, poly(vinyl acetate) presents a random monomer sequence distribution along the macromolecule chains, and this provides microdomains with different mobilities. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2457–2461, 1998

Dielectric effects of step-increased pressure on the mass- and diffusion-controlled linear chain and network macromolecules growth

The dielectric properties of four stoichiometric liquid mixtures of a diepoxide with two monoamines and two diamines have been studied in real time during the mixture's polymerization isothermally to a linear-chain polymer in two cases and a network polymer in the other two cases, at 1 and 200 bar. The pressure was applied: (a) at the beginning of polymerization, (b) after a small extent of polymerization when the viscosity was low, and (c) after a relatively large extent of polymerization when the viscosity was high. For a fixed polymerization period, pressure increased the dielectric relaxation time much more than any other quantity in all cases, without a change in the distribution of relaxation times. Contributions to the dielectric permittivity and loss from physical and chemical effects have been considered and related to the changes in the dielectric relaxation time, viscosity and polymerization-rate constant as the extent of polymerization increased with time. Pressure is expected to decrease the polymerization rate for all conditions, but the decrease is relatively insignificant at the early stage, when polymerization is mass-controlled. Here other effects override the effect of viscosity increase, and the polymerization rate instead increases. The decrease in the rate becomes significant and predominates only when polymerization becomes diffusion-controlled. Since theories of diffusion-controlled reactions do not consider the mutual slowing of the molecular diffusion and the rate of chemical reactions leading to a macromolecule's growth until its vitrification isothermally, a method for determining the onset of diffusion control was needed. It is shown that this onset can be determined from plotting the rate of polymerization against the dielectric relaxation time. Expressed in terms of the dielectric loss, these plots cross each other. The cross-over point indicates the onset of diffusion control. Thus, the effect of pressure on the dielectric behaviour can be used to determine the change from mass-controlled to diffusion-controlled kinetics.

Primitive models of chemical association. III. Totally flexible sticky two-point model for multicomponent heteronuclear fixed-chain-length polymerization

A multidensity integral-equation theory for polymerization into freely jointed hard-sphere homonuclear chain fluids proposed earlier [J. Chem. Phys. 106, 1940 (1997)] is extended to the case of multicomponent heteronuclear chain polymerization. The theory is based on the analytical solution of the polymer Percus–Yevick (PPY) approximation for the totally flexible sticky two-point (S2P) model of associating fluids. The model consists of an n-component mixture of hard spheres of different sizes with species 2,…,n−1 bearing two sticky sites A and B, randomly distributed on its surface, and species 1 and n with only one B and A site per particle, respectively. Due to some specific restrictions imposed on the possibility of forming bonds between particles of various species, the present version of the S2P model represents an associating fluid that is able to polymerize into a mixture of heteronuclear chain macromolecules. The structural properties of such a model are studied in the complete-association limit and compared with computer-simulation results for homonuclear hard-sphere chain mixtures, symmetrical diblock copolymers, alternating copolymers, and homonuclear hard-sphere chains in a hard-sphere solvent. Some results for the case of partial association are also presented. The PPY theory represents a quantitatively successful theory for the mixtures of short homonuclear chains and the short copolymer systems studied here. We also expect that the theory will prove to be of the same order of accuracy in investigating the case of partial association.

Synthesis and Investigation of Properties of the Optically Transparent Carbochain Copolymers with Elementorganical and Hydroxy Groups in the Side Chain of Macromolecules

The carbochain co-polymers with elementorganical and hydroxy groups in the side chain of macromolecules have been synthesized. The reactions of the radical co-polymerization of perfluoroalkyl(meth)acrylates and siliconorganic methacrylates with dimethylvinylacetylenylcarbinol in mass were studied. By using NMR-1H spectroscopy of high resolution, UV, IR spectroscopy and GLC methods the structure and the composition of co-polymers, constants of copolymerization rijrji , the distribution of homo and heterodiads in macromolecular chain of the co-polymers were determined. The optical, thermomechanical properties and the thermooxidative stability of the co-polymers were researched. The possibility of their application for production of the optical adhesives was determined.

Chiral Solvation as a Means to Quantitatively Characterize Preferential Solvation of a Helical Polymer in Mixed Solvents

Poly(n-hexyl isocyanate) adopts a helical structure in solution and the preference of one helical sense induced by a nonracemic chiral solvent can be detected by the circular dichroism (CD) of the backbone chromophore of the polymer. Addition of an achiral or racemic cosolvent leads to a reduction of the CD intensity, which can be interpreted quantitatively as reflecting the composition of the solvent mixture in contact with the helical backbone of the polymer. Equilibrium constants characterizing the relation between the solvent composition in contact with the polymer and the bulk of the system are given for mixtures of (S)-1-chloro-2-methylbutane and a number of achiral or racemic cosolvents. The relationship between the structure of the cosolvent and the extent of the preferential solvation was surprising in several instances. The polymer was preferentially solvated by a highly branched hydrocarbon although it was a precipitant and the preferential solvation by alcohols extended up to the point of polymer precipitation. This unusual method for characterizing preferential solvation of this rod-like polymer is compared with other methods used previously on flexible chain macromolecules.

Fokker–Planck equation for the one-molecule distribution function in polymer mixtures and its solution

It is shown how a Fokker–Planck equation in the phase space of a single polymer molecule in a multicomponent mixture can be obtained from the Liouville equation in the phase space of a mixture of polymeric liquids. This result is a generalization of the Schieber–Öttinger equation for a dilute solution of a single polymer species in a solvent, or the Öttinger–Petrillo equation for nonisothermal systems. The Fokker–Planck equation is solved as a series in powers of a small parameter ε, thereby displaying quantitatively the deviation of the velocity distribution from the Maxwellian. It is then shown how moments of the singlet distribution function needed for the evaluation of the transport coefficients can be obtained. In addition, expressions for the first three moments of the Brownian force are developed. It is further shown how the present discussion is related to the Curtiss–Bird theory for multicomponent diffusion. Throughout the development the polymer molecules are modeled as arbitrary bead-spring structures, with all inter-bead forces (representing both intra- and intermolecular forces) derivable from a potential and directed along the bead–bead vectors. These models can describe flexible chain macromolecules, ring-shaped polymers, starlike polymers, and branched polymers.

Non-traditional Method of Synthesis of Organosilicon Polymers

The combined polymerization-condensation process-the non-traditional method of synthesis of siliconorganic polymers with organo-inorganic and inorganic main chains of macromolecules is reviewed.

Specific heat relaxation during macromolecule growth.

When dissimilar molecules in a liquid mixture react isothermally to form covalent bonds and linear chain macromolecules grow until the liquid vitrifies, the complex ${C}_{p}$ of the mixture measured for a fixed frequency decreases. The real component of this ${C}_{p}$ measured as a function of the number of covalent bonds formed, or macroscopic reaction time, shows a dispersionlike decrease and the imaginary component a peak. From these data, the evolution of structural relaxation time during the growth of the macromolecules has been determined and its formalism given.

The effects of covalent bonds on the localized relaxations in the glassy states of linear chain and network macromolecules

Dipolar relaxations in the glassy states of five molecular liquids and of their partially and completely polymerized structures, both linear chain and network types, were studied by dielectric measurements for a fixed ac frequency of 1 kHz. Calorimetric measurements were made to determine the number of covalent bonds formed at different instants of polymerization, and the results were combined with the dielectric data to investigate how the height of the relaxation peak indicating localized dipole diffusion changed as the number of covalent bonds in the spontaneously polymerizing material increased. The height, or strength, of the peak due to the localized relaxation process in the molecular liquid gradually decreased and the process approached extinction as the number of covalent bonds approached its limiting value. Concurrently, a new localized glassy state relaxation process evolved at a temperature with a peak 70–90 K above that of the one observed for the molecular state and its height increased and approached a constant value as the number of covalent bonds formed approached its limiting value. These changes were quantitatively similar for the five materials, irrespective of the structure of the macromolecular product. The extinction of the sub-Tg relaxation peak observed originally for the unreacted state has features in common with structural relaxation effects.

Computer simulation and molecular theory of self‐organization and mechanical properties of polymers

AbstractIn this contribution, we report on a study of the self‐organization of extended linear polymer chains into condensed globules using molecular dynamics methods. We have found that condensed chains (globules) are amorphous or crystalline depending on the interaction potential between constituents. Any structure is formed in several stages. The structures obtained were used in further computer simulations to investigate such processes as compression, decompression, fracture, and flow. We have found that there are different types of fracture and plastic behavior with their own energy, fluctuation, and defect characteristics. On the basis of the computer simulation results obtained, the equation of motion is derived for the system of chain macromolecules slipping relative to each other. The equation takes into account the relaxation and friction in the system. The solution obtained gives the general law that connects stress, strain rate, molecular mass, potential relief, and temperature. It also gives sound physical grounds for some empirical relations that are used in polymer technology.

Monte Carlo study of semiflexible living polymers.

We study the order-disorder phase transition and the cluster-size distribution of ``living polymers'' in a lattice-hole model of a polydisperse system of semiflexible chain macromolecules by Monte Carlo simulation. In two dimensions we find that the transition line in T-\ensuremath{\mu} space (temperature--chemical potential) contains a tricritical point and that the values of the critical exponents along the second-order portion of the phase boundary belong to the Ising universality class. In three dimensions a finite-size scaling analysis suggests that the phase transition is always first order. In both cases the chain lengths of the polymers follow an exponential probability distribution although the dependence of the mean chain length on density and temperature deviates from predictions of analytical theory. (c) 1995 The American Physical Society

Crystallization kinetics for semicrystalline random copolymers of vinylidene chloride (VDC) with methyl acrylate (MA), and the effects on the internal morphology of the resin particles formed during synthesis

AbstractIsothermal crystallization kinetics for random copolymers of vinylidene chloride (VDC) with methyl acrylate (MA) is reported. Syntheses of many semicrystalline polymers follow heterogeneous reaction paths in which the macromolecule chains phase separate from the reaction mixtures. The internal particle morphology (the internal structure of the resin bead) from this type of reaction is granular and porous, as a result of the demixing processes accompanying polymer formation. Demixing in these polymers involves either liquid‐liquid (L‐L) phase separation followed by liquid‐solid (L‐S) transformation (crystallization) or L‐S transformation alone. Crystallization (L‐S transformation) must be an indispensable part of the process if a porous granular structure is to be expected. This is because L‐S transformation is the most probable means by which the demixed structure can be stabilized against complete coalescence or agglomeration, which would lead to totally fused bead internal structure. This is particularly true if the glass transition temperature (Tg) is lower than the polymerization temperatures, as is the case with the VDC‐MA copolymers. Copolymers that crystallize the fastest will have the finest (most porous) resin bead morphology. The result of this work is consistent with expectation. The homopolymer (PVDC) that crystallizes the fastest has the finest resin bead internal morphology. The copolymers show slower crystallization rates with increasing noncrystallizable MA content. Correspondingly, resin morphology measured by specific surface area decreased with increasing amounts of the noncrystallizable (MA) comonomer unit in the copolymer. This is clearly seen in SEM photographs of the internal bead structures of these copolymers. ©1995 John Wiley & Sons, Inc.

Heterofunctional Condensation of 4,6-bis(n-aminophenyl)pyrimidine with α,ω)-bis(diethylamino- and α,ω-bis(β-carboxylethyl)diorganosiloxanes

Abstract Copolymers containing siloxane fragments and aromatic heterocycles in their main chains of macro-molecules have been synthesized. Heterofunctional condensation of 4,6-bis(n-aminophenyl)pyrimidine with α,ω-(diethylamine)- and α,ω-bis(β-carboxylethyl)diorganosiloxanes was conducted at 1:1 molar ratio of initial components at 150–180°C. Thermogravimetric characteristics of the synthesized thermally stable copolymers have been investigated.

Photochemistry Synthesis and Characterization of Benzocycloheptan‐1,5‐Dione Derivatives

AbstractSome new benzocycloheptan‐1,5‐diones derivatives I (3: R = t‐Bu, R' = H; 4: R = Ph, R' = H; 5: R = PhCOCH2, R' = H; 6: R = CH3COCH2, R' = H; 7: R = t‐Bu, R' = ethenyle and 8: R = Ph, R' = ethenyle) were synthetized through photocycloaddition of 2‐acylindan‐1,3‐diones 2 with styrene and paradivinylbenzene (pDVB) respectively.The reaction proceeds regioselectively at the endocyclic enol. This regioselectivity was not observed on the linear β‐triketones, previously reported [1]. The formation of a double addition product paradi‐(2,5‐dioxo‐6‐(2,2‐dimethylpropionyl)‐benzocycloheptyl)‐benzene 9 shows how a network could be formed if these 2‐acylindan‐1,3‐diones 2 moities are graft in side chains of macromolecules. The enolic equilibrium of the obtained benzocycloheptan‐1,5‐ diones derivatives, are discussed. Every products were characterized by means of elemental analysis and IR, UV, 1H and 13C NMR spectroscopies.