Thermal degradation of vinylidene chloride/[4-(t-butoxycarbonyloxy)phenyl]methyl acrylate copolymers

Vinylidene chloride polymers containing comonomer units capable of consuming evolved hydrogen chloride to expose good radical-scavenging sites might be expected to display greater thermal stability than similar polymers containing simple alkyl acrylates as comonomer. Incorporation of a comonomer containing the phenyl t-butyl carbonate moiety into a vinylidene chloride polymer has the potential to afford a polymer with pendant groups which might interact with hydrogen chloride to expose phenolic groups. Copolymers of vinylidene chloride with [4-(t-butoxycarbonyloxy)phenyl]methyl acrylate have been prepared, characterized, and subjected to thermal degradation. The degradation has been characterized by thermal and spectroscopic techniques. The degradation of vinylidene chloride/[4-(t-butoxycarbonyloxy)phenyl]methyl acrylate copolymers is much more facile than the same process for similar copolymers containing either [4-(isobutoxycarbonyloxy)phenyl]methyl acrylate or methyl acrylate, a simple alkyl acrylate, as comonomer. During copolymer degradation, [4-(t-butoxycarbonyloxy) phenylmethyl acrylate units are apparently converted to acrylic acid units by extensive fragmentation of the sidechain. Thus, the phenyl t-butyl carbonate moiety does function as a labile acid-sensitive pendant group but its decomposition in this instance leads to the generation of a phenoxybenzyl carboxylate capable of further fragmentation.     

Synthesis of cyclo‐olefin copolymer latexes and their carbon nanotube composite nanoparticles

An efficient and environmentally benign synthetic method for the production of the stabilized cyclo‐olefin copolymer latexes and their carbon nanotube composite nanoparticles has been developed using an emulsion ring opening metathesis copolymerization catalyzed by the 2nd generation Grubbs catalyst in aqueous solution. Homopolymerizations of norbornene (NB) and dicyclopentadiene (DCPD) in aqueous solution yield unstable polymer latexes in combination with a large amount of their flocculation fractions. Copolymerizations of NB or DCPD with a selected liquid cyclo‐olefin comonomer dramatically improve not only the colloidal stability of the copolymer latexes but also the thermal stability of the copolymer nanoparticles. The liquid cyclo‐olefin comonomer plays a double role as a liquefied agent for the solid NB and DCPD monomers before the emulsification treatment, and a reactive comonomer itself to control entirely the copolymerization system. The as‐prepared cyclo‐olefin copolymer latexes exhibit an exceptionally high compatibility with a well‐dispersed carbon nanotube (CNT) in aqueous solution due to strong π–π interactions between the graphitic surfaces of the CNT with the C‐C double bonds located on the cyclo‐olefin copolymer main chains. Accordingly, a binary blending of these two well‐dispersed colloidal systems in aqueous solution led to the fabrication, for the first time, of the highly electrical conductive cyclo‐olefin copolymer/CNT composite nanoparticles. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4584–4591     

Preparation of highly sulfonated polystyrene model colloids

Previous attempts to prepare monodisperse styrene/sodium styrene sulfonate copolymer latexes by batch, seeded, and semicontinuous emulsion polymerization were unsuccessful at high concentrations of the functional comonomer. Broad, and sometimes bimodal, size distributions, and large amounts of water soluble homopolymer were obtained. After removal of free monomer, solute and adsorbed homopolymer and copolymer, the overall incorporation of the functional comonomer was found to be low. To overcome these problems, a two stage “shot-growth” or in situ seeding technique was developed. A first stage copolymerization was carried out with a low concentration of sodium styrene sulfonate: the purpose of the functional comonomer was to enhance the stability and regulate the size of the seed particles. When this reaction had reached high conversion (> 90%), a second stage monomer mixture was added. The ratio of styrene to sodium styrene sulfonate in this mixture determined the final surface charge density. The mechanism by which the NaSS is incorporated in the polymer particles is considered to be by solution copolymerization with solute styrene monomer to form surface active oligoradicals. These radicals adsorb on the particle surface, initiate polymerization and become inextricably bound, preventing their transfer back to the aqueous phase. By this means, it was possible to vary independently the particle size and surface charge density. High concentrations of functional comonomer could be polymerized without undue wastage (incorporations were only slightly less than 100%) or loss of monodispersity. In extreme cases, the area per functional group fell below the theoretical minimum, indicating considerable hydration of the surface layers.     

End‐functionalized copolymers prepared by the addition–fragmentation chain‐transfer method: Vinyl acetate/methacrylonitrile system

Copolymers of vinyl acetate and methacrylonitrile were prepared by free‐radical polymerization in the presence of the chain‐transfer agent (CTA) ethyl‐α‐ (t‐butanethiomethyl)acrylate. Molecular weight measurements showed that the chain‐transfer constants increased with the vinyl acetate content of the comonomer mixture, ranging from 0.42 for methacrylonitrile to 6.3 for the copolymerization of a vinyl acetate‐rich monomer mix (89/11). The bulk copolymer composition was not appreciably affected by the amount of CTA used in the copolymerization. The efficiency of the addition–fragmentation mechanism in producing specifically end‐functionalized copolymers was investigated with ¹H NMR spectroscopy. Spectral peaks consistent with all the expected end groups were observed for all comonomer feeds. Peaks consistent with other end groups were also observed, and these were particularly prominent for copolymers made with lower CTA concentrations. At the highest concentrations used, quantitative measurements of end‐group concentrations indicated that 70–80% of the end groups were those expected on the basis of the addition–fragmentation chain‐transfer mechanism. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2911–2919, 2001     

Effect of Endfunctionality of Reactive Polymers on the Reaction Kinetics at Immiscible Polymer Interfaces: A Monte Carlo Study

Reactions at the interface of two immiscible polymers containing different reactive groups at either one end or both ends are studied with Monte Carlo (MC) simulations. The MC simulation shows that the copolymer concentration at the interface is shown to dramatically increase during the early stage of reaction and then levels off at a constant value. The effect of endfunctionality, i. e., the effect of the number of endfunctional groups, is also investigated. While the saturation value of interfacial coverage is proportional to the initial reactive polymer density for the case of mono‐endfunctional polymer, the simulation results with di‐endfunctional polymers show that the saturation copolymer coverage is not exactly proportional to the initial reactive polymer density in the case of high concentrations of the initial reactive polymer. This is believed to be caused by the change of conformation of block copolymers formed at the interface due to reaction: the fraction of loop conformation decreases while the tail fraction increases with a large amount of initial reactive di‐endfunctional polymer. Also, the experimentally determined time‐dependent interfacial fracture toughness, which is, in turn, related to the copolymer coverage at the interface, is in good qualitative agreement with the simulation results.     

In situ compatibilization of PET/PS blends through carbamate‐functionalized reactive copolymers

To investigate the effect of reactive compatibilization in the immiscible poly(ethylene terephthalate) (PET)/polystyrene (PS) blend, poly(styrene‐co‐methacryloyl carbamate) (PSM) was synthesized as a reactive compatibilizer. The interfacial reaction of the carbamate group in PSM with OH/COOH in PET was confirmed by atomic force microscopy. The interfacial roughness developed rapidly with an increase in the methacryloyl carbamate (MAC) content and then leveled off above the optimum content (3.8 wt %). These results were well‐reflected in the interfacial adhesion, morphology, and mechanical properties of the PET/PS blends, showing a maximum value at the optimum MAC content. The existence of a maximum value is believed to stem from a reciprocal relationship between the sufficient formation of in situ copolymer and the fast diffusion rate of reactive polymers at the interface. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1396–1404, 2000     

Studies on microstructure and aqueous solution properties of block copolymer of acrylamide-styrene

Three series of block copolymers of acrylamide (AM) and styrene (St) as hydrophobic comonomer with varied microstructures were prepared in microemulsion medium by changing feed ratio of monomers, ratio of St to surfactant, and amount of initiator, respectively. The effects of microstructure factors of the amphiphilic block copolymers PAM-b-PSt on their aqueous solution properties were investigated by fluorescence probe technique and surface tension measurement in detail. The experimental results show that the aqueous solution properties of PAM-b-PSt are strongly dependent on their microstructure factors, such as the length and content of PSt hydrophobic blocks in the copolymers and their molecular weight. It was found that the main microstructure factors which effect the hydrophobic association behavior of the copolymer PAM-b-PSt are the length and content of PSt hydrophobic blocks in the copolymer, whereas the hydrophobic association behavior of the copolymer is not affected nearly so much by molecular weight in more dilute regions. At the same time, it was also found that the main microstructure factors which affect the surface activity of the copolymer are the content of PSt hydrophobic blocks in the copolymer and molecular weight, whereas the length of PSt blocks in copolymer does not affect surface activity of the copolymer nearly so much under fixed content of PSt hydrophobic blocks and molecular weight in the copolymer.     

Pendant groups fine‐tuning thermal gelation of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) aqueous solution

Novel poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) (PCL‐PEG‐PCL) bearing pendant hydrophobic γ‐(carbamic acid benzyl ester) groups (PECB) and hydrophiphilic amino groups (PECN) were synthesized based on the functionalized comonomer γ‐(carbamic acid benzyl ester)‐ε‐caprolactone (CABCL). The thermal gelation behavior of the amphiphilic copolymer aqueous solutions was examined. The phase transition behavior could be finely tuned via the pendant groups, and an abnormal phenomenon occurred that the sol–gel transition temperature shifted to a higher temperature for PECB whereas a lower temperature for PECN. The micelles percolation was adopted to clarify the hydrogel mechanism, and the effect of the pendant groups on the micellization was further investigated in detail. The results demonstrated that the introduction of γ‐(carbamic acid benzyl ester) pendant groups significantly decreased the crystallinity of the copolymer micelles whereas amino pendant groups made the micelles easy to aggregate. Thus, the thermal gelation of PEG/PCL aqueous solution could be finely tuned by the pendant groups, and the pendant groups modified PEG/PCL hydrogels are expected to have great potential biomedical application. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2571–2581     

Interfacial properties of diblock copolymers at penetrable interfaces: Density profile,stretching, and interfacial tension

The interfacial properties of diblock (AB) copolymers near an interface between two solvents are studied by using the exact Green's function of a Gaussian copolymer chain at an attractive penetrable interface. We have studied the mean‐square end‐to‐end distance of the copolymer, 〈R²(z)〉, as a function of the distance of the joint point of the copolymer to the interface, z, the segment density distribution ρ(z), and the reduction of the interfacial tension Δγ_c due to the presence of the diblock copolymer. The density profile and the stretching of the copolymer chain are in agreement with both experimental results and simulations. The reduction in the interfacial tension is found to decrease with the increase in the degree of polymerization of the copolymer chain.     

Characterization of semicrystalline random copolymers by small-angle neutron scattering

A new method is introduced to determine the degree of partitioning of noncrystallizable comonomer units (B units) between the two phases of a semicrystalline random copolymer. The method is based on the comparison of the intensities of small-angle neutron and x-ray scattering (SANS and SAXS, respectively). By this technique two quantities can be evaluated: the difference Δρ of the mass densities between the crystalline and the disordered regions, and the concentration fluctuations of the B units in the two phases. It is found that SANS is very sensitive to the presence of small amounts of B units if their scattering length is sufficiently different from that of the A units. This will be the case for copolymers with B units, in which a hydrogen is substituted by another atom. But in addition it can also be achieved generally by deuteration of the comonomer units. So a wide range of copolymer systems can be studied by this method. The capability of the method was proved by measurements on chlorinated polyethylene and on 1,3,5-trioxane–1,3-dioxolane copolymers. Both copolymers are distinguished by a random distribution of the co-units. The results show that even at relatively low concentrations x_B of the comonomer units a remarkable fraction of the B units is incorporated into the crystalline A phase and that this fraction rises if x_B is increased.     

Thermal stability of poly(mono-n-alkylitaconates) and mono-n-alkylitaconate-co-vinylpyrrolidone copolymers I

Poly(monoitaconates) containing octyl, decyl and dodecyl groups and random monoalkylitaconate-co-vinylpyrrolidone copolymers were studied by thermogravimetric analysis. Copolymers of mono-n-octylitaconate (MOI), mono-n-decylitaconate (MDI), and mono-n-dodecylitaconate (MDoI), respectively, with N-vinyl-2-pyrrolidone (VP) of different compositions were studied by dynamic thermogravimetric analysis. The thermal stability of the copolymers depends on the structure of the monoitaconate comonomer and on the composition of the copolymer The kinetic analysis of the degradation data shows that the thermal decomposition of these copolymers can be described by several kinetic orders depending on the copolymer and on the composition. The relative thermal stability of the copolymers increases as the VP content increases and as the length of the side chain of the itaconate increases, following the same trend as the flexibility of the copolymers in solution.     

Synthesis of biocompatible and biodegradable polymer particles in supercritical carbon dioxide

The free radical copolymerization of N-vinyl-2-pyrrolidone and 2-methylene-1,3-dioxepane was carried out in supercritical carbon dioxide (scCO₂) using three kinds of dispersants and 2,2′-azobisisobutyronitrile as the initiator. Polymerization was performed with fluorinated polymeric dispersants synthesized in scCO₂ using the solution polymerization method and commercially available siloxane-based surfactant. Spherical biocompatible and biodegradable polymeric particles were prepared within the sub-micron size range. The effect of various ratios of the comonomer, reaction temperature, and concentration of initiator, in addition to the types and concentrations of the dispersants, on the particle size and morphology was investigated. The particle size and particle size distribution of copolymer particles were controlled using the above mentioned experimental parameters. Glass transition temperatures of copolymers were varied according to the comonomer ratios used.     

Some Reactions of Vinyl Isocyanate and Its Copolymers∗

Linear, soluble copolymers of vinyl isocyanate with styrene and methyl methacrylate were obtained when the comonomer:vinyl isocyanate ratio in the copolymer was greater than 9:1. When the comonomer to isocyanate ratio was less than 2:1, the copolymers were insoluble. Infrared evidence indicated that spontaneous cross-linking through the isocyanate function occurred by a mechanism similar to the known reaction by which isocyanates undergo dimerization and trimerization. The soluble copolymers retained the reactive isocyanate moeity as was shown by their reactivity with n-butylamine and ethanol to produce, respectively, the corresponding polyurea and polycarbamate, and with ethylenediamine and water to produce cross-linked polymers. The intrinsic viscosity [η] for the 9:1 methyl methacrylate: vinyl isocyanate copolymer was 0.22 dl/g while that for the corresponding ethyl carbamate was 0.24 dl/g.     

Characterization of ethylene/propylene copolymers by means of a GPC-4D technique

Copolymer composition and comonomer distribution are important magnitudes in polymer material that have a big effect on different kind of properties and consequently there are several ways to study.In this work several ethylene/propylene copolymers synthesized with two different metallocene catalysts and a Ziegler–Natta catalyst and covering a wide composition range were studied. Characterization was carried out by nuclear magnetic resonance (¹³C NMR) and by gel permeation chromatography with 4 detectors (GPC-4D): refractive index, viscosity, multi-angle light scattering and infrared detectors.Different behaviour in the comonomer distribution along the molecular weight was obtained for metallocene and for ZN copolymers as expected due to the differences between these catalytic systems. Nevertheless, Ziegler–Natta copolymers present more homogeneous comonomer distribution due to the synthesis method. Study of conformation of chains in solution was improved by defining the scaling law of R_g against the number of repeat units because it avoids the effect of the repetitive unit size. Both metallocene copolymer sets show similar dependence of q value with the copolymer composition, however Ziegler–Natta copolymers show different behaviour with q values independent on copolymer composition. This different behaviour has been related with the effects of the heterogeneity of the ethylene distribution and of the molecular weight of the samples.     

“Protein‐Like” Copolymers: Effect of Polymer Architecture on the Performance in Bioseparation Process

Recently, a new class of copolymers, so‐called protein‐like copolymers has been predicted theoretically by computer simulation. In these copolymers, the conformation of the copolymer determines the exposure of certain comonomer units to the outer solution. Depending on the conformation, copolymer molecules with essentially the same comonomer composition could have pronouncedly different properties. The authors demonstrated experimentally such behavior in case of poly[(N‐vinylcaprolactam)‐co‐(N‐vinylimidazole)] (Dokl. Chem. 2001 , 375, 637). One more group of copolymers with protein‐like behavior is copolymers of N‐isopropylacrylamide with N‐vinylimidazole. Poly[(N‐isopropylacrylamide)‐co‐(N‐vinylimidazole)] was synthesized by radical polymerization and separated into two fractions using immobilized metal affinity chromatography on Cu²⁺‐loaded iminodiacetic acid sepharose CL 6B (Cu²⁺‐IDA‐sepharose). The unbound fraction which passed through the column and bound fraction eluted with Ethylenediaminetetraacetic acid, disodium salt (EDTA) solution differed significantly in molecular weight, 1.4×10⁶ and 1.35×10⁵, respectively but were very close in comonomer composition, 7.8 and 9.1 mol‐% of imidazole, respectively. The composition of bound fraction was confirmed by titration of imidazole groups. Despite close chemical composition, the bound and unbound fraction behaved differently with respect to temperature‐induced phase separation at different pH values, the dependence of hydrodynamic diameter on pH and concentration of Cu²⁺‐ions, and the coprecipitation of soybean trypsin inhibitor with the copolymer in the presence of Cu²⁺‐ions. The differences in the behavior of copolymer fractions are rationalized assuming that the bound fraction presents a protein‐like copolymer.     

Synthesis and thermochemistry of phenylmaleimide- and phenylnadimide-terminated bisphenol A polycarbonates

Phenylmaleimide (PMI)- and phenylnadimide (PNI)-terminated bisphenol A polycarbonates (PCs) were prepared by solution or interfacial phosgenation processes, and their thermal crosslinking, both with and without a free radical initiator, and the thermal stability of the resultant network polymers were investigated. m-PMI PCs were prepared by interfacial phosgenation of bisphenol A and m-hydroxyphenylmaleimide, but p-hydroxyphenylmaleimide caused rapid phosgene hydrolysis under interfacial conditions and PCs from it could only be made by solution phosgenation. The degree of crosslinking of PMI PCs, as measured by their gel fraction, heated in the absence of a free radical initiator was generally higher at 250°C than at 300°C and increased with the concentration of PMI end groups. m- and p-PMI PCs form thermosets having nearly complete gel fractions by radical initiated curing at 150–200°C. The gel fraction of these thermosets decreases with exposure to higher temperatures (300°C). This behavior is attributed to BA PC chain degradation induced by nitrogen-containing maleimide reaction products. p-PNI PC was prepared by solution phosgenation and the thermal reaction of it in the presence of the initiator produced only a small increase in molecular weight. © 1997 John Wiley & Sons, Inc.     

Synthesis of styrene–acrylamide copolymer by surfactant‐free sonicated dynamic interfacial polymerization

This paper summarizes a study on emulsifier‐free ultrasonically assisted in situ dynamic interfacial emulsion copolymerization process of acrylamide and styrene. The resulting emulsions are stable and uniform for several months. Thermogravimetric analysis (TGA) curves and reaction conversion measurements have provided an important knowledge regarding the emulsifier‐free polymerization method. Solvent extractions (water, methanol, and xylene) have shown that the polymerization product is essentially a styrene–acrylamide copolymer. The copolymer produced is a block copolymer, PS‐b‐PAM, where each block contains small amounts of the other comonomer. The produced emulsions are film forming at room temperature in spite of the very high block T_gs, owing to a unique water plasticization effect of the polyacrylamide blocks. Some films prepared from the PS‐b‐PAM have resulted in clear and transparent films. The presented interfacial dynamic polymerization process is fast, reaching 81% conversion within 2 hr of sonication at 4°C (low temperature owing to molecular weight and kinetic considerations), and produces very stable PS‐b‐PAM emulsions. TGA was extensively used as an analytical tool for determination of the reaction parameters and composition of the acrylamide–styrene copolymers. Copyright © 2011 John Wiley & Sons, Ltd.     

An experimental study on saturation swelling of styrene–acryronitrile copolymer particles with styrene and acrylonitrile monomers

The saturation swelling behavior of styrene and acrylonitrile (SAN) copolymer particles with a styrene (St) and acrylonitrile (AN) comonomer mixture was investigated experimentally. The effects of the copolymer composition and the compositional inhomogeneity in SAN Copolymer particles on their swelling behavior were examined. The experimental results show that both the copolymer composition and the compositional inhomogeneity in SAN copolymer particles have little or no influence on the swellability of SAN copolymer particles with a St and AN comonomer mixture, as long as the weight fraction of AN monomer units in SAN copolymer particles is less than a certain value between 0.6 and 0.8. With increasing AN content in the copolymer particles beyond this value, however, the swellability of SAN copolymer particles gradually decreases. Semiempirical equations are proposed, which correlate the saturation concentration of each monomer in SAN copolymer particles as a function of the comonomer composition in the monomer droplets and the overall copolymer composition in SAN copolymer particles. © 1994 John Wiley & Sons, Inc.     

Phase behavior of blends of linear low density polyethylene and poly(ethene-propene-1-butene)

The aim of this work was the study of blends of linear low density polyethylene (LLDPE) and an ethene-propene-1-butene terpolymer (t-PP). Two types of polyethylene were used to prepare the blends: an ethene-co-1-hexene (LLDPE(H)) copolymer and an ethene-co-1-octene (LLDPE(O)) copolymer. These copolymers present similar comonomer contents, molar mass, molar mass distribution and catalyst systems, but differ in their comonomer distribution. The blends were obtained through mechanical mixing using a single screw extruder at different compositions: 20, 40, 50, 60 and 80 wt.% of LLDPE. From DSC measurements two separated melting and crystallization peaks were observed and dynamic mechanical analysis showed two glass transitions indicating that LLDPE/t-PP blends are immiscible in amorphous and crystalline phases in the solid state. X-ray diffraction showed that the unit cell parameters of both polymers in the blends remain unchanged independent of the composition of the blend.     

Structure–property transition‐state model for the copolymerization of ethene and 1‐hexene with experimental and theoretical applications to novel disilylene‐bridged zirconocenes

Ethene homopolymerization and copolymerization with 1‐hexene were performed with three new tetramethyldisilylene‐bridged zirconocene catalysts with 2‐indenyl ligand ( A ), 2‐tetrahydroindenyl ligand ( B ), and tetramethyl‐cyclopentadienyl ligand ( C ) and with methylaluminoxane as a cocatalyst. Catalysts A and B showed substantial comonomer incorporation, resulting in a copolymer melting temperature more than 20° lower than that of the corresponding homopolymer. In contrast, catalyst C produced a copolymer with a low 1‐hexene content and a high melting temperature. The reduction in the molecular weight with 1‐hexene addition also correlated well with the comonomer incorporation. For all three catalysts, the homopolymer and copolymer unsaturations indicated frequent chain termination after 1‐hexene insertion and a high degree of chain‐end isomerization during the homopolymerization of ethene. The chain transfer to Al in the cocatalyst also appeared to be important. The comonomer response could be correlated with the structural properties of the catalyst, as derived from quantum chemical calculations. A linear model, calibrated against recent experiments with unbridged (Me_nC₅H_5?n)₂ZrCl₂ catalysts, suggested that the low comonomer incorporation obtained with catalyst C was caused partly by a narrow opening angle between the aromatic ligands and partly by steric hindrance in the transition state of comonomer insertion. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1622–1631, 2003