Treating the polyelectrolytes as polymers with a draining effect. II. The behavior in the gel permeation chromatography

The behavior of the polyelectrolytes in the gel permeation chromatography (GPC) can be better understood if the modified universal calibration (log([η]M/Φ) vs. elution volume) is used instead of the “classical” universal calibration (log[η]M vs. elution volume). The value of Flory's parameter Φ is obtained from an equation established for nonionic polymers presenting a draining effect, considering that polyelectrolytes also behave as polymers with a draining effect. The modified universal calibration does not apply as successfully to polyelectrolytes as to nonionic polymers, because of their electrostatic exclusion in the pore surface of the GPC columns. Nevertheless, when polyelectrolytes are found in a high salt concentration solution, the modified universal calibration can be used to obtain their molecular mass, using nonionic hydrosoluble polymers as standard polymers. Moreover, considering polyelectrolytes as polymers presenting a draining effect and applying the modified universal calibration provides a better explanation for the electrostatic exclusion of these polymers from the pores of the GPC columns, using the Dubin–Tecklenburg model. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1106–1113, 2006     

New high temperature polymers. VI. Ordered heterocycle copolymers

A new class of linear, thermostable polymers is reported. The compositions are ordered heterocycle copolymers in which two different heterocycles alternate regularly along the polymer chain. Examples of combinations studied are: oxadiazole–benzimidazole, oxadiazole–pyromellitimide, and thiazole–pyromellitimide. The heterocycle copolymers, or alternatively, the corresponding precursor polymers, were prepared by condensing preformed di-or tetrafunctional blocks which contain one type of heterocycle with a second di- or tetrafunctional monomer under such conditions that no rearrangement of bonds occurred. The polymers are characterized in general by neither melting nor decomposing below 500°C. when heated in an inert atmosphere at a rate of about 10°C./min. Some of the copolymers are readily soluble in organic solvents; many, however, are soluble only in solvents such as concentrated sulfuric acid. In the case of the more intractable polymers, soluble precursor polymers can usually be prepared. In such precursor polymers only one of the heterocycles is preformed; the second heterocycle is formed by post-treatment after the polymer has been fabricated into an end product. All of the polymers yielded self-supporting films, some having very high strength; films of several of the polymers were hot-drawable. Drawn film of an ordered oxadiazoleimide copolymer was shown to be well oriented and moderately crystalline.     

Chemical Reactions on Polymers. II. Modification of Diene Polymers with Triazolinediones via the Ene Reaction

A wide variety of polymers and copolymers of 1,3-dienes have been modified at low temperatures via the ene reaction with 4-substituted l,2,4-triazoline-3,5-diones. The resulting modified polymers were characterized via infrared spectroscopy, nuclear magnetic resonance, intrinsic viscosity, gel-permeation chromatography, differential scanning calorimetry, solubility tests, and tensile measurements. Physical properties measurements support the postulate that the highly polar pendant urazole groups contribute inter molecular and intramolecular hydrogen-bonding interactions and thus impart to the modified polymers thermoplastic elastomer properties. Changes in the solubility character, thermal behavior, and tensile properties of the modified polymers are in accord with this postulate. Since the association between molecules is physical in nature, the modified polymers remain soluble in appropriate solvents. They also show dramatic decreases in molecular size; for example, the average molecular size of polymers at 1% modification is about one tenth that of the unmodified polymer due to intramolecular interactions, a size reduction of the same order of magnitude as that of chemically crosslinked polymers. Poly-1,2-butadiene, when modified to the extent of 5%, gave values for elongation to break, Young's modulus, and tensile strength twice those for the parent polymer, while tensile recoveries were > 90%.     

Four-center type photopolymerization in the solid state. III. Polymerization of phenylene diacrylic acid and its derivatives

The solid-state photopolymerization of phenylene diacrylic acid (PDA) and its derivatives was studied as an application of solid-state photodimerization of cinnamic acid to photopolymerization of corresponding bifunctional molecule which has two cinnamic units in a single molecule. p- and m-PDA, and their esters and amides were prepared and investigated with respect to their photopolymerizability. Many of them have been found to polymerize into linear high polymers with the cyclobutane rings in the main chain on irradiation by ultraviolet or visible light. The polymerization process, the structure of the polymers, and their general properties were investigated in several ways. All the polymers are very similar to poly-2,5-distyrylpyrazine and poly-1,4-bis(β-pyridyl-2-vinyl) benzene with respect to their polymerization behavior, polymer structure, and some polymer properties: these polymers are soluble in a limited number of solvents, they have a high melting point and an extremely high crystallinity. On the basis of chemical behavior of poly-PDA and its phenyl ester the possible steric configurations of these polymers are discussed. It is demonstrated for the PDA series that solid-state dimerization can be generally extended to solid-state photopolymerization of the compound having two dimerizable units in a single molecule, although the crystal structure renders polymerization impossible in certain cases.     

Analysis of the π-electronic structure of infinitely large networks. I. Some remarks on the characteristic polynomial and density of states of large polycyclic aromatic hydrocarbons

General expressions of the characteristic polynomials of various series of cyclic and linear polymers of polycyclic aromatic hydrocarbons are presented, i.e., polyacene, zigzag-polyacene, 1,4-dimethylbenzene polymer, polyperylene, etc. The densities of states of cyclic and linear polymers with the same repetitive units are shown. In some cases the allowed region of the energy levels of these polymers is found not to be the same. Several related problems are discussed.     

Chemical modification of polymers. XI. Photoreactive polymers from poly(vinylbenzyl chloride)

Photocrosslinking has been observed in a number of polymers derived by chemical modification of poly(vinylbenzyl chloride). Included are polymers bearing pendant benzophenone, stilbazolium, fluorenone, carbazole, and sulfonylazido moieties. The synthesis and properties of these polymers are described.     

Living polymers. Their discovery,characterization, and properties

The story of the discovery of living polymers is presented. Living polymers are polymers that retain their ability to propagate and grow to a desired size while their degree of termination or chain transfer is still negligible. Theoretical and mechanistic considerations are discussed. The living polymerization technique provides access to uniform polymers (Poisson molecular weight distribution) of controllable size, block copolymers, functional polymers, and star and comb-shaped polymers. The quantitative aspects of electron transfer are fully discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: ix–xv, 1998     

Polymers with quinoxaline units. IV. Polymers with quinoxaline and oxazine units

Six ladder or partly ladder polymers have been prepared by the condensation of diaminodiphenols with tetrachloro- or terahydroxyquinoxaline derivatives with the use of poly (phosphoric acid), pyridine, and naphthalene as reaction media. The polymers thus obtained are highly colored powdery materials which are slightly soluble in concentrated sulfuric acid and methanesulfonic acid. These polymers show good thermal stability.     

On the structure of glassy polymers. VI. Electron microscopy of polycarbonate,poly(ethylene terephthalate), poly(vinyl chloride), and polystyrene

High-resolution electron microscopy studies have been carried out on four glassy polymers examined in previous small-angle x-ray scattering (SAXS) investigations. The polymers include polycarbonate, poly(ethylene terephthalate), poly(vinyl chloride), and polystyrene. For all four polymers, both bright field and dark-field observations indicate the general absence of microstructural features of a size down to the resolution limit of the electron microscope. Only “pepper and salt” features on a scale ca. 5 Å are seen as characteristic of the structures. These features reflect simple interferences as the resolution limit is approached, and are seen for single crystal and oxide glasses as well as for the polymers. The present results, taken together with structural information from light scattering, SAXS, and small-angle neutron scattering, indicate that glassy polymers should be regarded as having rendom structures. The combined results are inconsistent with heterogeneous microstructures having regions of locally high order present in large volume fractions.     

Photopolymerization via the Paterno-Büchi reaction. I. Reaction of aromatic diketones with tetramethylallene

Aromatic diketones of the benzophenone type undergo photopolymerization on irradiation at 350 nm with tetramethylallene in benzene solution. The polymers produced contain oxetane units in the main chain, and spectroscopic analysis demonstrates that the distribution of structural units parallels that found in the reaction between benzophenone and tetramethylallene. The polymers are rapidly degraded thermally and by mineral acids.     

Luminescence studies in polymers-IX. Polarization of the fluorescence of copolymer films

Energy migration has been directly demonstrated to be very efficient in solid polymers by studying the depolarization of the fluorescence of copolymer films as a function of composition. The results are compared with those obtained for the same copolymers in glassy solution. They indicate that migration is more important in bulk polymers than in dilute glassy solutions owing to intermolecular interactions in agreement with the structural models proposed for amorphous polymers.     

Plasma polymerization. XI. A comparison of the plasma polymerization of the isomeric perfluorinated diazines

Plasma polymers synthesized by inductively coupled RF techniques have been investigated as a function of operating parameters for the isomeric perfluorinated diazines (pyrazine, pyrimidine, and pyridazine). A combination of ESCA and microanalytical studies shows that plasma polymers are produced by rearrangement mechanisms: the C/F and C/N stoichiometric ratios are similar to those of the starting monomers over a range of operating parameters. A comparison of rates of formation of plasma polymer films reveals distinctive differences between the isomeric diazines that suggest that equilibration of valence isomers occurs on a substantially slower time scale than for isomeric fluorinated benzenes^5–9 which, in general, polymerize at essentially the same rates. In contrast to the remarkably low critical surface tension of plasma polymers based on perfluorobenzenes (ca. 20 dynes cm^?2), the plasma polymer films from the perfluorinated diazines which are initially hydrophobic become hydrophilic in contact with water droplets. This is attributed to the hydrolytic instability of films associated with the labilizing influence of nitrogen on nucleophilic displacement of fluoride which is a feature of the chemistry of monomers.     

Polymeric Schiff Bases. VII. Some Parameters in the Evaluation of the Thermal Stability of Poly(p-Xylylidene-p-phenylenediamine)

Thermogravimetric analyses of poly(p-xylylidene-p-phenylenediamine) in nitrogen, helium, and air yield stability values substantially identical to values obtained from tests in vacuo. The respective thermal stability values in nitrogen and in air are unchanged over a fourfold change in gas flow rates. Slightly lower values are found at heating rates of 5–15°C/min than at 30°C/min. Thermal stabilities are lower in oxygen than in air, but the values are still relatively high. Higher apparent thermal stability values are observed when a powder sample of 10 mg is evaluated as a single mass rather than as a fine powder. Calorimetric measurements indicate that Schiff base polymers which have been heated in nitrogen to 1000–1200°C have not been converted to graphite-type polymers. The Schiff base polymers are resistant to radiation; their stability is shown to be independent of dose rate and of the nature of the ionizing radiation.     

Plasma synthesis of polymers. A comparison of inductively coupled RF and microwave plasmas excited in the isomeric difluoroethylenes

A preliminary investigation of polymers prepared by RF and microwave glow discharge techniques is described. The polymer composition structure as revealed by ESCA is discussed and differences are shown to be subtle rather than major. Microwave prepared polymers are more sensitive to the operating conditions than the corresponding RF prepared polymers.     

Polydimethylsiloxane–vinyl block polymers. II. The synthesis and characterization of block polymers by the thermolysis of polydimethylsiloxane macroinitiators containing bis(silyl pinacolate) groups

The thermolysis of polydimethylsiloxanes containing thermally labile bis(silyl pinacolate) groups in the backbone in the presence of various vinyl monomers leads to the direct synthesis of block polymers. Depending on the monomer chosen, simple triblock or multisequence block polymers can be readily prepared. Analysis of the products of the block polymerizations using various styrenic-type monomers shows that only block polymers are obtained, i.e., no homo-polymers are formed. These block polymers display evidence of phase separation such as intense iridescence and solvent-dependent mechanical properties. The mechanical properties of these block polymers have been measured and found to be highly composition dependent. Depending on the block length and the relative portions of the hard (vinyl) and soft (polydimethylsiloxane) blocks, one can produce either thermoplastic elastomers or rubber-modified thermoplastics.     

Plasma polymerization. VII. An esca investigation of the RF plasma polymerization of perfluorobenzene and perfluorobenzene/hydrogen mixtures

The composition and gross structural features of plasma polymers formed in the glow regions of an inductively coupled RF plasma with perfluorobenzene and perfluorobenzene/hydrogen mixtures were investigated by ESCA as a function of the operating parameters. The carbon-to-fluorine stoichiometries of the perfluorobenzene polymers are similar and close to those of the starting material but not of the polymers derived from perfluorobenzene/hydrogen mixtures. The rate of film deposition is dependent on the W/FM parameter. Angular and photon energy-dependent studies confirm the vertical homogeneity of the plasma polymer films investigated.     

Polymer additive analysis by pyrolysis-gas chromatography. IV. Antioxidants

Antioxidants are important additives in polymers. Because of the low level of antioxidants normally used, they cannot be analyzed directly by common spectroscopic or thermal chemical techniques. However, antioxidants as well as other additives in polymers can be qualitatively analyzed by pyrolysis-gas chromatography (Py-GC) after separating the polymers and additives. In this study, several antioxidants have been investigated to demonstrate that Py-GC is a viable tool to analyze them. The advantages of using Py-GC in the analysis of antioxidants have also been discussed.     

Polyether azomethines. I. Synthesis and characterization

Six new polyether azomethines were synthesized by melt and solution polycondensation of six different diamines with 4,4′-[1,4-phenylene bis(oxy)] bisbenzaldehyde. The polymers synthesized by solution method are yellow to white in color and had inherent viscosities up to 0.59 dL/g in concentrated H₂SO₄. The polymers obtained by melt condensation show higher viscosity. Except polymer IV , others are insoluble in common organic solvents. The polymers were characterized by IR, x-ray, elemental analysis, and DSC study. The thermal stability of the polymers was evaluated by TGA and IGA study. Polymers I-III are highly thermally and thermooxidatively stable and exhibit no appreciable decomposition up to 420°C both in air and nitrogen atmosphere. It was shown that the curing of the polyazo-methines takes place by opening up of the ? CH?N? linkages at higher temperature. The electrical conductivities of the virgin and iodine doped polymers were as high as 10^?11?10^?16 and 10^?6?10^?8S cm^?1, respectively, at 30°C. Electronic spectra of the undoped polymers ( I-III ) indicated a large bathochromic shift of the ? – ?^* absorptions band (376 nm) due to ? C?N? bonds of the model compound. This can be attributed to extensive delocalization of the electrons along the polymer chain. © 1995 John Wiley & Sons, Inc.     

Liquid crystal polymers. XVIII. Comparison of the properties of aromatic polyesters with different mesogenic units and a common flexible spacer

Four closely related polyesters, with aromatic ester triads and decamethylene spacers, were prepared and characterized for their thermotropic liquid crystalline properties. Two of the polymers, which were based on linear biphenols, formed stable nematic phases, whereas one of the two based on nonlinear biphenols formed a poorly defined nematic phase; the other was not liquid crystalline. Several polymerization reactions and methods were evaluated and structure-property relationships of the polymers are discussed. The concept of “degree of liquid crystallinity” for polymers with poorly defined thermotropic behavior is considered.