Characterization and degradation of poly(vinyl chloride-g-lsobutylene) carrying tertiary chlorine and cyclopentadienyl branch termini

Summary Poly(vinyl chloride-g-isobutylene)s have been synthetized by using PVC backbones containing relatively high concentration of allylic chlorines [PVC(A)] in conjunction with BCl₃ coinitiator. Since graft-termination occurs by ion-collapse, graft copolymers with tertiary chlorine branch termini [PVC(A)-g-PIB-Cl] were formed. The presence of terminal tertiary chlorines has been demonstrated by degradation and cyclopentadienylation experiments. UV-visible spectra of ungrafted and grafted PVC(A) , molecular weight data, and branching frequency as a function of concentration of allylic chlorines indicate chain transfer to polyenes. Thermal and thermooxidative stability of PVC(A) increases upon grafting due to the replacement of allylic chlorines by PIB branches. The introduction of highly oxidizable Cp groups in PVC(A)-g-PIB-Cl by Me₂CpAl-treatment decreases the thermooxidative stability.     

Grafting of poly(vinyl chloride) and polypropylene with styrene in a supercritical CO2 solvent medium: Synthesis and characterization

Graft copolymerization of styrene onto poly(vinyl chloride) (PVC) and polypropylene (PP) was carried out in a supercritical CO₂ medium using AIBN as a free radical initiator. The supercritical CO₂ medium served as a reaction medium in addition to being a solvent for the styrene monomer and the free radical initiator. The reaction temperature and pressure were kept above the critical points of the solvent‐monomer mixture to form a homogeneous single‐phase medium. The resulting graft copolymers were characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and nuclear magnetic resonance (NMR) techniques. The weight percent of grafting was determined using IR absorbance ratio technique. TGA results showed that the thermal stabilily of grafted copolymer of PVC was better than that of PVC, while grafted copolymer of PP had poorer thermal stability than PP. DSC results showed that glass transition temperatures (T_g's) of the grafted copolymers were higher than those of the starting polymers PVC and PP. The presence of polystyrene attached to the backbone polymer was confirmed by ¹H NMR and ¹³C NMR analyses.     

Internal plasticization of poly(vinyl chloride) by grafting acrylate copolymers via copper-mediated atom transfer radical polymerization

Internal plasticization of poly(vinyl chloride) (PVC) was achieved in one-step using copper-mediated atom transfer radical polymerization to graft different ratios of random n-butyl acrylate and 2–2-(2-ethoxyethoxy)ethyl acrylate copolymers from defect sites on the PVC chain. Five graft polymers were made with different ratios of poly(butyl acrylate) (PBA) and poly(2–2-(2-ethoxyethoxy)ethyl acrylate) (P2EEA); the glass transition temperatures (T_g) of functionalized PVC polymers range from − 25 to − 50°C. Single T_g values were observed for all polymers, indicating good compatibility between PVC and grafted chains, with no evidence of microphase separation. Plasticization efficiency is higher for polyether P2EEA moieties compared with PBA components. The resultant PVC graft copolymers are thermally more stable compared to unmodified PVC. Increasing the reaction scale from 2 to 14 g produces consistent and reproducible results, suggesting this method could be applicable on an industrial scale.     

Waste‐reducing preparation of PE‐g‐MAH and PE‐g‐DBM via solid phase grafting reaction and their application as compatibilizers

Kinetics for grafting two reactive monomers (dibutyl maleate (DBM) and maleic anhydride (MAH)) on polyethylene (PE) was investigated for the modified PE (PE‐g‐MAH and PE‐g‐DBM) using solid phase grafting process. This process avoided solvent waste produced in solution process and high operation temperature in melt process. In the presence of the radical initiator, coupling reactions, between the PE and product, and macromolecular radicals, routinely form gels and/or increase molecular weight, resulting in a worse rheological behavior for the grafting products. By adding small amount of interface agents, using combined initiators and optimizing reactor design, graft copolymers with controlled grafting degrees and good rheological properties were prepared. The grafting degrees of copolymers were determined by chemical analysis. FTIR, DSC, and pure water contact angle characterized the chemical structure, the thermal property, and the hydrophilic property of the grafting copolymers, respectively. The peel strength of the graft copolymer as powder coating on the stainless steel surface was measured as high as 12–24 kgf/cm. Mechanical strength and toughness of PE/kaolin clay, PVC/CPE, and PVC/CPE/CaCO₃ alloys with small amount of the graft copolymer (～5 wt %) added were improved significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3781–3790, 2006     

Cationic grafting of norbornadiene, indene, and 1,3-cyclohexadiene from PVC

Summary The synthesis of three novel graft copolymers consisting of a PVC backbone fitted with polynorbornadiene (PNbd), polyindene (PInd), polycyclohexadiene (PCHD) branches, i.e., PVC-g-PNbd, PVC-g-PInd, and PVC-g-PCHD, is described. The synthesis strategy was to initiate the grafting of norbornadiene (Nbd), indene (Ind), and 1,3-cyclohexadiene (CHD) by a PVC containing ∼ 1.6 active (tertary and allylic) chlorines in conjunction with Et₂AlCl. The products were characterized by solvent fractionation, molecular weight determination, T_g, and NMR spectroscopy. The effect of temperature on the grafting was investigated in the 20 to −50 °C range. Received: 8 October 2001/ Revised version: 22 April 2002/ Accepted: 23 April 2002     

Development of a new azido-oxazoline monomer for the preparation of amphiphilic graft copolymers by combination of cationic ring-opening polymerization and click chemistry

A new monomer (2-(5-azidopentyl)-2-oxazoline) bearing an azido group was synthesized. The cationic ring-opening copolymerization of this monomer with 2-methyl-2-oxazoline resulted in a well-defined linear polymer backbone with pendant azido groups. Alkynyl-poly(d,l-lactide) was grafted onto the azido groups of poly(oxazoline) via a Huisgen 1,3-dipolar cycloaddition reaction to give a novel amphiphilic graft copolymer [poly(2-methyl-2-oxazoline-co-2-pentyl-2-oxazoline)-g-poly(d,l-lactide)] (P[(MeOx-co-PentOx)-g-LA]). Different graft copolymers were prepared with PLA of different lengths. Preliminary results of the self-association of this copolymer in water indicated the formation of nanoparticles, which suggests this copolymer may have applications as vehicles for drug delivery.     

Synthesis,characterization, and enhanced antibacterial activity of chitosan‐based biodegradable conducting graft copolymers

In this study, synthesis, characterization, and antibacterial activity of chitosan‐based biodegradable conducting graft copolymers namely polyaniline‐g‐chitosan, polypyrrole‐g‐chitosan, and polythiophene‐g‐chitosan with chemical oxidation method using (NH₄)₂S₂O₈ and FeCl₃ as initiators were investigated. Characterizations of the materials were carried out by means of Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, UV–vis, thermogravimetric analysis, scanning electron microscope, transmission electron microscope, and temperature‐dependent electrical conductivity measurements. The grafting yield, grafting efficiency, particle sizes, dielectric constants, and densities of the conducting graft copolymers were determined. Grafting process improved the conductivities and thermal stabilities of the copolymers. The conducting polymer‐g‐chitosan copolymers were also tested against Klebsiella pneumoniae, Escherichia coli, Bacillus megaterium, Enterococcus faecalis, Staphylococcus aureus microorganisms and relatively higher or equipotent antibacterial activities were determined against the microorganisms compared with Penicillin, Amikacin, Erythromycin, Rifampicin, and Trimethoprim antibiotics. POLYM. COMPOS. 36:497–509, 2015. © 2014 Society of Plastics Engineers     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers)

Summary Linear and three-arm star tosyl-telechelic polyisobutylenes (i.e., PIB's carrying two and three p-toluene-sulfonic acid ester end groups, respectively) have been synthesized and characterized by a variety of techniques. Subsequently these prepolymers were used as macroinitiators for the ring opening polymerization of 2-methyl-2-oxazoline leading to linear poly(N-acetylethyleneimine-b-isobutylene-b-N-acetylethyleneimine) and three-arm star poly(N-acetylethyleneimine-b-isobutylene). High yields (78–98%) and blocking efficiencies (70–80%) have been obtained. The absence of free polyisobutylene in the product indicates highly efficient initiation of 2-methyl-2-oxazoline polymerization by the tosyl-telechelic polyisobutylene. The less than 100% blocking efficiencies are probably due to chain transfer to 2-methyl-2-oxazoline. Hydrolysis of these block copolymers yielded poly(ethyleneimine-b-isobutylenes).Present address: Department of Macromolecular Science, Case Western Reserve University, Cleveland, Ohio 44106.Present address: Central Research Institute for Chemistry, Hungarian Academy of Sciences, Budapest, Hungary.     

Synthesis of palladium clusters with surface initiator for polymerization of 2-methyl-2-oxazoline

Summary Palladium clusters were synthesized by reduction of palladium(II) acetate in the presence of a bipyridyl ligand (1) with an initiator for polymerization of 2-methyl-2-oxazoline. The 1-protected palladium clusters were soluble in CHCl₃ and CH₂Cl₂. The 1-protected palladium clusters were combined with 2-methyl-2-oxazoline in chloroform. After polymerization, the reacted bipyridyl ligand was removed from the palladium cluster by suspending the obtained palladium clusters with pyridine. The ¹H NMR measurement indicated that the reacted bipyridyl ligand was formed via surface polymerization of 2-methyl-2-oxazoline. Received: 19 April 2001/Accepted: 2 May 2001     

Competitive removal of heavy metal ions by cellulose graft copolymers

The effect of composition of graft chains of four types cellulose graft copolymers on the competitive removal of Pb²⁺, Cu²⁺, and Cd²⁺ ions from aqueous solution was investigated. The copolymers used were (1) cellulose‐g‐polyacrylic acid (cellulose‐g‐pAA) with grafting percentages of 7, 18, and 30%; (2) cellulose‐g‐p(AA–NMBA) prepared by grafting of AA onto cellulose in the presence of crosslinking agent of N,N′‐methylene bisacrylamide (NMBA); (3) cellulose‐g‐p(AA–AASO₃H) prepared by grafting of a monomer mixture of acrylic acid (AA) and 2‐acrylamido‐2‐methyl propane sulphonic acid (AASO₃H) containing 10% (in mole) AASO₃H; and (4) cellulose‐g‐pAASO₃H obtained by grafting of AASO₃H onto cellulose. The concentrations of ions which were kept constant at 4 mmol/L in an aqueous solution of pH 4.5 were equal. Metal ion removal capacities and removal percentages of the copolymers was determined. Metal ion removal capacity of cellulose‐g‐pAA did not change with the increase in grafting percentages of the copolymer and determined to be 0.27 mmol metal ion/g_copolymer. Although the metal removal rate of cellulose‐g‐p(AA–NMBA) copolymer was lower than that of cellulose‐g‐pAA, removal capacities of both copolymers were the same which was equal to 0.24 mmol metal ion/g_copolymer. Cellulose did not remove any ion under the same conditions. In addition, cellulose‐g‐pAASO₃H removed practically no ion from the aqueous solution (0.02 mmol metal ion/g_copolymer). The presence of AASO₃H in the graft chains of cellulose‐g‐p(AA–AASO₃H) created a synergistic effect with respect to metal removal and led to a slight increase in metal ion adsorption capability in comparison to that of cellulose‐g‐pAA. All types of cellulose copolymers were found to be selective for the removal of Pb²⁺ over Cu²⁺ and Cd²⁺. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2034–2039, 2003     

Amination of glycidyl methacrylate-grafted polystyrene particles and their adsorption capacity for Nd3+ and Cd2+

A new chelating adsorbent was prepared by grafting glycidyl methacrylate (GMA) onto polystyrene (PS) particles using simultaneous radiation technique and amination of graft copolymers by reacting with diethylenetriamine. The effects of various parameters such as, irradiation doses, inhibitor concentrations, amination temperature, and reaction time were investigated. The grafting yield increased with irradiation dose to reach its maximum value at 15 kGy. The accelerative effect of solvent medium on the grafting yield was higher in THF than DMF. The addition of 0.001 % (wt) inhibitor to the reaction medium led to a sharp increase of grafting yield. The best conversion ratio was obtained at 115 °C during 24 h. By using a column separation technique, the adsorption behaviors of the adsorbent toward Cd²⁺ and Nd³⁺ in aqueous solution were examined. The adsorption amount of both Cd²⁺ and Nd³⁺ increased with initial ions concentration. The maximum equilibrium of Cd²⁺ and Nd³⁺ adsorbed ions were 18.1 and 17.58 mg/g, respectively. It was observed that the functionalized GMA-g-PS was reusable by desorbing with 0.1 M nitric acid almost without losing their adsorption capacity. FTIR test indicates that epoxide and amine groups were introduced onto GMA-g-PS and aminated GMA-g-PS, respectively. The T _g of graft copolymer slightly decreased, and that of aminated GMA-g-PS was higher than graft copolymer.     

Thermoresponsive Molecular Brushes with a Rigid-Chain Aromatic Polyester Backbone and Poly-2-alkyl-2-oxazoline Side Chains

A new polycondensation aromatic rigid-chain polyester macroinitiator was synthesized and used to graft linear poly-2-ethyl-2-oxazoline as well as poly-2-isopropyl-2-oxazoline by cationic polymerization. The prepared copolymers and the macroinitiator were characterized by NMR, GPC, AFM, turbidimetry, static, and dynamic light scattering. The molar masses of the polyester main chain and the grafted copolymers with poly-2-ethyl-2-oxazoline and poly-2-isopropyl-2-oxazoline side chains were 26,500, 208,000, and 67,900, respectively. The molar masses of the side chains of poly-2-ethyl-2-oxazoline and poly-2-isopropyl-2-oxazoline and their grafting densities were 7400 and 3400 and 0.53 and 0.27, respectively. In chloroform, the copolymers conformation can be considered as a cylinder wormlike chain, the diameter of which depends on the side chain length. In water at low temperatures, the macromolecules of the poly-2-ethyl-2-oxazoline copolymer assume a wormlike conformation because their backbones are well shielded by side chains, whereas the copolymer with short side chains and low grafting density strongly aggregates, which was visualized by AFM. The phase separation temperatures of the copolymers were lower than those of linear analogs of the side chains and decreased with the concentration for both samples. The LCST were estimated to be around 45 °C for the poly-2-ethyl-2-oxazoline graft copolymer, and below 20 °C for the poly-2-isopropyl-2-oxazoline graft copolymer.     

Photografting of PVC containing N,N‐diethyldithiocarbamate groups with vinyl monomers

Poly(vinyl chloride) (PVC) with pendent N,N‐diethyldithiocarbamate groups (PVC–SR) was prepared through the reaction of PVC with sodium N,N‐diethyldithiocarbamate (NaSR) in butanone and used as a photoinitiator for the grafting polymerization of three vinyl monomers [styrene (St), methyl methacrylate (MMA), and acrylamide (Am)]. The effects of ultraviolet (UV) irradiation time, PVC–SR amount, and the monomer amount on grafting and grafting efficiency were investigated. The results showed that PVC–SR could initiate the polymerization of three vinyl monomers effectively and obtained crosslinked copolymers. The grafting and grafting efficiency of styrene and methyl methacrylate were higher than those of acrylamide. The polymerization activity of three monomers was acrylamide > methyl methacrylate > styrene. By analyzing the UV spectrum of PVC–SR with a different irradiation time, it was confirmed that PVC–SR was dissociated mainly into macromolecular the sulfur radical PVC–S · and the small molecular carbon radical · C(S)N(C₂H₅)₂; the grafting polymerization mechanism was discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2569–2574, 2000     

Mechanical properties of poly(vinyl chloride) blends and corresponding graft copolymers

The mechanical properties of the poly (vinyl chloride) (PVC) and poly (glycidyl methacrylate) [poly (GMA)] blend system and the PVC and poly (hydroxyethyl methacrylate) [poly (HEMA)] blend system and their crosslinked films were investigated. At the same time, the mechanical properties for the corresponding graft copolymers such as PVC-g-GMA, PVC-g-HEMA, and their crosslinked films were also investigated in this study. The results showed that the tensile strengths for PVC–poly (GMA) blend systems were higher than those for PVC-g-GMA graft copolymer, and the tensile strengths for PVC-g-HEMA were higher than those for PVC-poly (HEMA) blend systems. However, the mechanical properties for the PVC–poly (GMA) blend system were not affected by the crosslinking of the blend system, but those for PVC-poly (HEMA) and their graft copolymers decreased with an increase of the equivalent ratio ([NCO]/[OH]) of the crosslinker. Finally, the surface hydrophilicity of the PVC-g-HEMA graft copolymer and PVC-poly (HEMA) blends were also assessed through measuring the contact angle. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 307–319, 1998     

Synthesis and characterization of mica—vinyl graft copolymers

Graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto mica was carried out by the ceric ion method. Experiments were carried out both in the presence and absence of oxygen; oxygen has some detrimental effect in the grafting of AN onto mica. Mica—vinyl graft copolymers were characterized using infrared spectra after purifying the crude graft copolymers for the removal of the occluded homopolymers. The percent grafting, grafting efficiency and the ratio of R_g/R_h were determined. Mica—graft copolymers were saponified by treating with aqueous alkali to convert the nitrile groups to carboxyl groups with a view to utilize these groups for coupling to collagen substrates. Since in a chrome-tanned leather there are available coordination sites due to fixed chromium, the mica—graft copolymer could get bound, thereby resulting in a well filled-up leather.     

Copolymerization via zwitterion

Summary Copolymers of 2-methyl-2-oxazoline and phtalic anhydride without initiator were prepared at 60°C in DMF, CH₃CN and in bulk. The copolymers were statistical rich in 2-methyl-2-oxazoline and the -COCH₃ groups are partially hydrolized. The composition and the degree of hydrolysis of the copolymers were determined by ¹H-NMR. ¹³C-NMR proved that the hydrolisis did not occur during the polymerization process. A scheme of copolymerization via zwitterion is presented.     

Water-soluble copolymers. I. Synthesis of model dextran-g-polyacrylamides by Fe(II)/H2O2 initiation and characterization by aqueous size exclusion chromatography

Model graft copolymers were synthesized by grafting acrylamide onto dextran (M?_w = 500,000) utilizing the Fe(II)/H₂O₂ initiation system. Aqueous size exclusion chromatography (SEC) was used to determine the effects of changing reaction parameters on hydrodynamic dimensions of the resulting graft copolymers. It was also possible to optimize reaction conditions yielding the highest viscosity graft copolymer with the least amount of homopolyacrylamide and unreacted substrate. The molecular structures of the graft copolymers were determined by elemental analysis, SEC, and solution viscometry. Selective hydrolysis of the dextran backbone allowed determination of average molecular weight of acrylamide grafts, number of grafting sites, and average molecular weight of the graft copolymers. Rheological studies indicated viscosity and pseudoplastic behavior were largely related to the graft length of the polyacrylamide side chains.     

Synthesis of polypropylene graft copolymers from a hydroxyl‐groups‐containing polypropylene precursor via atom‐transfer radical polymerization

Isotactic polypropylene graft copolymers, isotactic[polypropylene‐graft‐poly(methyl methacrylate)] (i‐PP‐g‐PMMA) and isotactic[polypropylene‐graft‐polystyrene] (i‐PP‐g‐PS), were prepared by atom‐transfer radical polymerization (ATRP) using a 2‐bromopropionic ester macro‐initiator from functional polypropylene‐containing hydroxyl groups. This kind of functionalized propylene can be obtained by copolymerization of propylene and borane monomer using isospecific MgCl₂‐supported TiCl₄ as catalyst. Both the graft density and the molecular weights of i‐PP‐based graft copolymers were controlled by changing the hydroxyl group contents of functionalized polypropylene and the amount of monomer used in the grafting reaction. The effect of i‐PP‐g‐PS graft copolymer on PP‐PS blends and that of i‐PP‐g‐PMMA graft copolymer on PP‐PMMA blends were studied by scanning electron microscopy. Copyright © 2006 Society of Chemical Industry     

Dehydrochlorinated poly(vinyl chloride)-g-polystyrene. II. Characterization and physical properties

Dehydrochlorinated poly(vinyl chloride)-g-polystyrene (DHPVC-g-PSt) prepared by free radical grafting was characterized, and some of its physical properties were evaluated. The presence of graft was established by the appearance of new absorption peaks in the IR spectra of the graft copolymer. GPC analysis showed increase in the average molecular weights of the graft copolymer upon increase in the PSt content. Besides, GPC revealed the uniform PSt distribution of DHPVC-g-PSt. A marked improvement in the thermal stability of DHPVC-g-PSt over that of DHPVC and DHPVC/PSt blends was observed. Graft copolymers with high percent grafting were thermally more stable than even the original PVC. Stress–strain data indicated decrease in yield stress, breaking stress and elongation, along with an increase in the initial modulus, upon increase in PSt content of the graft copolymer.     

Synthesis,characterization, and swelling behavior of poly(N-hydroxymethylacrylamide) grafted poly(vinyl alcohol)

In this study, the graft copolymerization of N-hydroxymethylacrylamide (NHMAAm) with poly(vinyl alcohol) (PVA) was carried out by using potassium persulfate/N,N,N,N-tetramethylethylenediamine (K₂S₂O₈) to improve physicochemical properties and functionality of PVA. The structures of PVA-g-poly-NHMAAm (PNHMAAm) copolymers were characterized by Fourier transform infrared, elemental analysis, nuclear magnetic resonance (¹H-NMR), ¹³C-NMR, and size exclusion chromatography. Their thermal behaviors were investigated by differential scanning calorimetry and thermogravimetric analysis (TGA). The TGA results indicated that the graft copolymers show better thermal stability then PVA. The effects of reaction time, temperature, NHMAAm, and K₂S₂O₈ concentrations on grafting parameters were examined. The maximum grafting yield (34.01%) was provided when reaction was carried out under optimum conditions (time = 2 hr, T = 40°C, [NHMAAm] = 0.25 M, [K₂S₂O₈] = 4.56 × 10⁻³ M). Moreover, PVA-g-PNHMAAm membranes were prepared and their swelling behaviors were studied. The results demonstrated that swelling degree of graft membranes increased almost 3.5-fold compared to PVA membrane.