Spin-probe studies. II. Applications to polymer characterization

The spin-probe technique has been employed to study interactions between several small organic nitroxides and host polymers in which they are dissolved. By this method one is able to study the mobility of the dissolved molecule in its microscopic environment using electron spin resonance spectroscopy. The behavior of one nitroxide has been examined in twelve different polymers and copolymers. An ESR line shape parameter has been correlated with T_m and T_g. In addition, energy barriers for the rotation of the dissolved nitroxides in the polymers have been calculated. They range from 7.8 to 18 kcal/mole, depending on the structure of the nitroxide and the polymer. Similar experiments in a hydrocarbon solvent afford a rotational energy barrier of 3.8 kcal/mole.     

Polymeric Nitrofuran Derivatives. I. Radical-Initiated Homo- and Copolymerization of 5-Nitrofurfuryl Methacrylate

The radical homopolymerization of 5-nitrofurfuryl methacrylate (NFMA) and the copolymerization of NFMA with methyl methacrylate and various vinyl monomers, respectively, have been studied in dimethylformamide at 65°C. NFMA and poly(NFMA) have been characterized by ¹H-NMR, IR, and UV spectroscopy. The influence of polymerization conditions on monomer conversion and on the molecular weight of the polymers obtained has been investigated. The thermal behavior of the polymers obtained has been studied by TGA and DSC analysis.     

Degradation of polymer mixtures. VI. Blends of poly(vinyl chloride) with polystyrene

The degradation of films containing both PS and PVC has been examined by TVA and TG. Stabilization of both polymers, more notably PS, is observed, but the degradation products are the same as when the polymers are degraded alone. Molecular weight measurements indicate a more rapid decrease in the molecular weight of PS when PVC is present. The possibility of grafting or other processes leading to chlorine incorporation in PS has been excluded by the results of experiments using ³⁶Cl-labeled PVC. The mechanisms of possible interactions between the degrading polymers are discussed. Processes involving reaction of chlorine radicals with PS at lower temperatures and reaction of PS radicals with the residue of PVC dehydrochlorination or its decomposition products at higher temperatures appear probable.     

The oxyluminescence of polymers. A review

A review of the oxyluminescence of polymers is presented here. When polymers are heated in an air or oxygen atmosphere, they exhibit a low-level light emission called oxyluminescence (OL). This new phenomenon has been used to study the oxidative degradation of polymers as well as to evaluate stabilizer concentration and behavior. This review consists of the following: (a), OL intensity and spectral distribution; (b), mechanism of the OL process; (c), kinetics of OL; (d), OL in polymer stabilizer studies; (e), instrumentation; and (f), polymers studied by OL.     

Sulfur-containing polymers. II. Preparation and properties of polycarbamoylsulfenamides

Polycarbamoylsulfenamides have been prepared by interfacial and solution polycondensation of chlorocarbonylsulfenyl chloride with diamines. In preparing the polycarbamoylsulfenamides, the following types of diamines were used: primary aliphatic diamines, a mixed primary-secondary aliphatic diamine, primary aromatic diamines, and secondary aromatic diamines. The properties of the resulting polymers depended primarily on the kind of diamines used. Transparent, tough films were obtained from the polymer based on N,N′-dimethyl-4,4′-diaminodiphenylmethane. The photochemical decomposition of the polymers has been studied.     

Copolyamide-imides of controlled microstructure. Effect of reaction conditions on regularity and properties

Aromatic polyamide-imides, based on trimellitimide and 4,4′-diphenylmethane and with different degrees of order, have been obtained from symmetric and asymmetric monomers. The polymers have been prepared by two general methods: (1) low temperature solution polycondensation of diamines and carboxylic acid derivatives; and (2) high temperature solution polycondensation of diisocyanates and dicarboxylic acids. High field ¹H-NMR has been used to elucidate the chemical structures of monomers and polymers and to estimate quantitatively the degree of order and the distribution of head-to-head, tail-to-tail (amide-amide, imide-imide) and head-to-tail (amide-imide) units. The influences of microstructure and other molecular features on some properties of the polymers have also been investigated.     

Haloaldehyde Polymers. XIV. Endgroups in Polychloral

Chloral polymers prepared by anionic polymerization have alkoxide endgroups as terminal ends at the end of this polymerization. The initiating anion has, as expected, no influence on the type of terminal group formed. Polychloral with terminal alkoxide ends degrades easily thermally to monomeric chloral. Alkoxide endgroups in polychloral do not readily react with alkylating or acylating agents, although partial stabilization has been observed when alkoxide-terminated polymers were allowed to stand for periods of time; the endgroups seem to react either with impurities or with excess chloral in side reactions. With protic acids, alkoxide-terminated polychloral is transformed into hydroxyl-terminated polymer of higher thermal stability. Studies of the initiation step of the chloral polymerization revealed that above the ceiling temperature of polymerization, strong nucleophiles, such as soluble tertiary butoxide, initiate quantitatively, but polymerization does not proceed until the mixture is cooled. When chloral is initiated with weaker nucleophiles such as chloride or carboxylates, the initiation equilibrium is not on the side of the initiated species, although it shifts effectively as polymerization proceeds; with carboxylates as initiators the ester group has been found incorporated as the initial endgroup in polychloral. With sufficient amounts of lithium tertiary butoxide as anionic initiator, polychloral of low molecular weight was prepared. This polymer does not react with end-capping reagents (other than PCl₅) as does high molecular weight polychloral; in spite of considerable effort it was not possible to prepare low molecular weight soluble polychloral or oligomeric polychloral. Polychloral prepared with cationic initiators is thermally more stable than unstabilized anionically initiated polychloral but is generally crumbly and incoherent. The end-groups of such polymers are usually hydroxyl endgroups. Identification of endgroups of the polymers has been done where possible by IR spectroscopy, for the initiation reaction by NMR spectroscopy, but for high molecular weight insoluble polymers almost exclusively by comparative thermal polymer degradation.     

Simulation of Molecular Weight Distribution After Polymer Breakdown. I. A Least-Squares Parameter Estimation Method on Monte Carlo Models

The degradation index (DI) has been used in previous work for Monte Carlo simulation of breakdown of polymers with narrow initial molecular weight distribution. However, the definition of DI is inadequate for polymers of broader molecular weight distribution. A least-squares method for estimating DI for such systems is described.     

Cyclopolymerization. VII. The 13C NMR Spectra of Cyclopolymers Obtained from N,N-Diallyamines

Pulsed Fourier transform ¹³C natural abundance nuclear magnetic resonance spectroscopy has been used to determine the structures of the polymers formed by the radical-induced cyclopolymerization of N-substituted-N, N-diallylamines and N-methyl-N, N-bls(2-alkylallyl)-amines. The polymers of N, N-diallylamines all contain cis-and trans-substituted pyrrolidine rings in the ratio 5:1. The polymers of N-methyl-N, N-bis(2-alkylallyl)amines give complex spectra due to the presence of both cis-and trans-pyrrolidine and -piperidine rings, but the difference in chemical shifts of the N-methyl signals from the different structural types allows the spectra to be analyzed.     

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 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.     

Thermally reversible polymer systems by cyclopentadienylation. II. The synthesis of cyclopentadiene-containing polymers

The synthesis of polymers containing either terminal or pendant cyclopentadiene (CPD) groups has been studied. Using information obtained from model studies, the synthesis of polyisobutylenes containing a CPD terminus was accomplished by the use of the tert-butylchloride–dimethylcyclopentadienylaluminum initiator system. Isobutylene polymerization by this system under carefully chosen conditions is essentially transfer free, and termination occurs by cyciopentadienylation. The presence of CPD end group has been established by UV spectroscopy and reaction with maleic anhydride. Selectivity toward termination by cyclopentadienylation increases with decreasing temperatures; at ?41°C and low conversion (<10%) ca. 72% of the polymer chains terminate in this manner. The synthesis of polymers containing randomly distributed pendant CPD groups along the chain has been accomplished by cyclopentadienylating with dimethylcyclopentadienylaluminum chlorobutyl rubber and chlorinated poly(ethylene-co-propylene) (Cl-EPM). Pendant CPD groups undergo Diels-Alder/retro-Diels-Alder condensations yielding thermally reversible networks; e.g., a cyclopentadienylated Cl-EPM was remolded three times to elastic sheets.     

Functional polymers. IX. Polycarbonates and alternating copolycarbonates of bithionol

A number of polycarbonates, alternating copolycarbonates, polyurethanes, and terpolymers with carbonate and/or urethane linkages utilizing bithionol [2,2'-thiobis(4,6-dichlorophenol)] as the bisphenol component of the polymers have been synthesized. Bithionol has been demonstrated to give a polycarbonate with an inherent viscosity of about 0.5 dl/g. The polycarbonate is amorphous and has a glass transition temperature T_g of about 105°C. Alternating copolycarbonates and polyurethanes involving bithionol are most conveniently prepared from the bischloroformate of bithionol. An alternating copolycarbonate of bithionol and poly(ethylene glycol) of molecular weight 4000 has an inherent viscosity of more than 1.2 dl/g, is water soluble, and has characteristics similar to those of low-density polyethylene. Alternating copolymers of bithionol and other hindered bisphenols have been synthesized and can be visualized as having an antibacterial agent and an antioxidant in the same polymer chain. These polymers have the potential to act as very useful materials for the controlled release of drugs while only forming carbon dioxide as the additional small molecule fragment on hydrolysis.     

Thermal degradation studies of substituted conducting polyanilines

The synthesis of conducting polymers based on m-nitroaniline, m-chloroaniline and m-aminophenol by aniline initiated ammonium peroxydisulfate oxidation, has been attempted. The IR spectra of the polymers have been studied. Thermogravimetric analysis of the conducting polymers has been followed using a computer analysis method LOTUS PACKAGE, developed by us for assigning the degradation mechanism. A number of equations have been used to evaluate the kinetic parameters. The mechanism of degradation of the conducting polymers has been explained on the basis of their kinetic parameters.     

Polyisobutylene-containing block polymers by sequential monomer addition. I. The living carbocationic polymerization of styrene

The living carbocationic polymerisation of styrene (St) has been investigated by the 2-chloro-2,4,4-trimethylpentane (TMPCI)/TiCl₄ initiating system in the presence of various additives such as electron pair donors (ED_s) and the proton trap 2,6-di-tert-butylpyridine (DtBP) by the use of the mixed solvent CH₃Cl/methyl-cyclohexane (MCHx) (40/60 v/v) at ?80°C under conventional laboratory conditions. The TMPCl/TiCl₄ system in the absence of additives produces ill-defined bimodal molecular weight distribution (MWD) polymers. Much better defined polystyrenes (PSt) can be obtained in the presence of EDs, such as N,N-dimethylacetamide (DMA) and hexamethylphosphoramide (HMPA). Monomer depletion should be avoided to prevent intra- or intermolecular alkylation yielding indanyl end groups or branched polymers, respectively. In the combined presence of an ED and the proton trap, i.e., DMA + DtBP, the living polymerization of St has been achieved and thus the foundations for the carbocationic synthesis of PSt block polymers by sequential monomer addition have been laid.     

Degradable Polymers. III. Synthesis and Characterization of Aliphatic Thermoplastic Block Copolyesters

A group of new block copolymers has been synthesized and characterized. The copolyesters were step-polymerized with six different poly-ether feeds, ranging from 21.1 to 53.3 mol%. The resulting polyethylene succinate)-b-poly(tetramethylene glycol) (PES/PTMG) polymers were characterized by GPC, DSC, IR, and NMR, and tensile strength measurements were performed. The molar composition of the polymers was determined by NMR and also correlated with IR. The compositions of the polymers agree well with those expected from the composition of the feed. Fibers for tensile strength measurements were extruded, and samples for dynamic mechanical tests (DMTA) were compression molded. The crystallinity, the melting temperature, the fiber strength, and the elastic bending modulus decreased with increasing polyether content, whereas the breaking strain increased.     

Synthesis of Aminotelechelic Polymers with the Redox System TiCl3/NH2OH in the Hydrochloric Aqueous Phase. I. Polymerization Possibilities and Limits

Among recent progress in the field of macromolecular chemistry, of considerable interest has been the synthesis of α, ω-ordifunctional polymers. These polymers, called “telechelic” polymers, are interesting because many reactions are possible on their functional end-groups:     

Poly-Schiff bases. III. Synthesis and characterization of polyesterazomethines

Ten new polyesterazomethines have been synthesized by solution polycondensation of five different diamines with 4,4′-[terephthaloyloxy]bis-3-ethoxybenzaldehyde and 4,4′-[isophthaloyloxy]bis-3-ethoxybenzaldehyde using dimethylacetamide in the presence of anhydrous LiCL. Fibrous polymers were precipitated by pouring the solutions into water. The polymerization proceeds rapidly to give highly viscous solutions. The resulting polymers were characterized by viscosity measurement, IR, x-ray diffraction study, elemental analysis, and DSC study. ¹H-NMR spectra of some of the polymers were also recorded. The thermal stability of the polymers was evaluated by TGA and IGA study. Electronic spectra of the polymers were recorded in H₂SO₄. © 1996 John Wiley & Sons, Inc.     

1,2-dinitrile polymers. III. Number-average molecular weight by pulsed NMR technique

In studies of various polymers in the solid state by pulsed and wide-line NMR, a relationship between the spin-lattice relaxation time and the fraction of mobile protons in the polymer sample was observed. This effect has been used to determine the degree of polymerization of a series of fumaronitrile homopolymers. The technique should have wide applicability in the direct determination of the number-average molecular weight M?_n, especially for polymers that may be insoluble and/or infusible though not crosslinked.     

Quinone-amine polymers. XII. Synthesis and characterization of novel polymers from 2-phenylbenzoquinone and aliphatic diamines

In order to study the effect of the presence of phenyl groups in poly (amino-quinone) (PAQ) polymers, several novel poly(amino-2-phenylbenzoquinone) (PhPAQ) polymers have been prepared from 2-phenylbenzoquinone and aliphatic diamines, such as 1,6-diaminohexane, 1,8-diaminooctane, 1,12-diaminodod+++++, and 1,4-diaminocyclohexane. Prior to the polymerization, 2-phenylbenzoquinone was generated in situ from 2-phenylhydroquinone in the presence of calcium hypochlorite as the oxidizing agent in dichloromethane. All of the polymers synthesized have been characterized with respect to their corresponding model compounds. It was also found that unlike their analogous PAQ polymers, PhPAQ polymers were highly soluble in many common organic solvents because of the presence of phenyl groups in their polymer backbone. © 1994 John Wiley & Sons, Inc.