Melt grafting of poly(ethylene‐vinyl acetate) copolymer with maleic anhydride

Poly(ethylene‐vinyl acetate) (EVA) copolymer was melt grafted with maleic anhydride (MAH) in a twin screw extruder in the presence of peroxide. It is confirmed that MAH has been melt grafted on the backbone of EVA by FTIR using the method of hydrolysis. The NMR analysis suggests that the grafting reaction occurs on the tertiary carbon of main chain of EVA other than the methyl moiety of vinyl acetate (VA) group. The incorporation of VA groups onto the matrix shows a competitive effect on the grafting. The existence of VA groups promotes the extent of MAH graft onto EVA; nevertheless, it also weakens the crystallizability of main chain. When the content of peroxide initiator is 0.1 wt % based on the polymer matrix, the grafting degree increases with increasing the concentration of monomer. When the peroxide content is higher than 0.1 wt %, side reactions such as crosslinking or disproportionation will be introduced into this system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 841–846, 2006     

Grafting and phosphonic acid functionalization of hyperbranched polyamidoamine polymer onto ultrafine silica

In this study, grafting of hyperbranched polyamidoamine (PAMAM) polymer onto ultrafine silica followed by functionalization via the introduction of phosphonic acid groups into the branch ends was performed. First, an initiating site was incorporated into the silica surface by reacting the silica silanol group with 3‐aminopropyltriethoxysilane, producing amino‐functionalized silica. The free amine group content was altered by varying the ratio of methanol to water in the hydrolysis step of the silanization reaction. Grafting of PAMAM was attained by three rounds of sequential Michael addition of silica amino groups to methyl acrylate and amidation of the resulting terminal methyl ester groups with ethylenediamine. Completion of the grafting reaction in each step was clearly confirmed using FTIR analysis. Excessive ethylenediamine and unattached hyperbranched PAMAM present in the reaction product were removed by dialysis with a molecular weight cutoff of 6000–7000 Daltons. However, the amino group content determined in each step was found to be significantly lower than theoretically expected, perhaps indicative of side reactions and, in later stages, steric hindrance. The resultant hyperbranched PAMAM‐grafted onto silica was functionalized by phosphorylation of the terminal amino groups by a Mannich type reaction, producing the phosphorylated hyperbranched PAMAM‐grafted silica. Then its application on cotton fabric to produce fire‐retardant cellulose was tentatively investigated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Graft polymerization of vinyl monomers initiated by peroxycarbonate groups introduced onto silica surface by Michael addition

The introduction of peroxycarbonate groups onto a silica surface and the graft polymerization of vinyl monomers initiated by peroxycarbonate groups introduced onto a silica surface were investigated. The introduction of peroxycarbonate groups onto a silica surface was achieved by Michael addition of amino groups introduced onto the silica surface to t‐butylperoxy‐2‐methacryloyloxyethylcarbonate (HEPO). The amount of peroxycarbonate groups was determined to be 0.17 mmol/g. The graft polymerization of various vinyl monomers such as styrene (St), N‐vinyl‐2‐pyrrolidinone (NVPD), and 2‐hydroxyethyl methacrylate (HEMA) was initiated by peroxycarbonate groups introduced onto the silica surface to give the corresponding polymer‐grafted silicas. The percentage of poly(St)‐grafting reached about 120% after 5 h. This means that 1.20 g of poly(St) is grafted onto 1.0 g of silica. The surface of poly(St)‐grafted silica shows a hydrophobic nature, but the surfaces of poly(NVPD) and poly(HEMA)‐grafted silica show a hydrophilic nature. Furthermore, the poly(St)‐grafted silica was found to give a stable colloidal dispersion in a good solvent for the grafted polymer. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1491–1497, 1999     

Crosslinking of PET through solid state functionalization with alkoxysilane derivatives

A new way for crosslinking poly(ethylene terephthalate) (PET) films and fibers is described using solid state functionalization of the PET end groups (alcohol and acid) with two reagents, respectively, 3-isocyanatopropyltriethoxysilane (IPTESI) or/and 3-glycidoxypropyltrimethoxysilane (GOPTMSI). This functionalization is then followed by hydrolysis-condensation reactions of PET-alkoxysilane end groups leading to the PET crosslinking.First of all, the functionalization reactions were investigated on model compounds by ¹H NMR spectroscopy in a range of temperature 80-160 °C. Furthermore, the diffusion of reagents in solid PET, depending on the initial degree of PET crystallinity, was characterized in the same temperature range through the variation of sample mass. On the other hand, this method allowed us to determine the diffusion coefficients and the solubility of the reagents in solid PET at different temperatures and initial crystallinity degrees.End groups functionalized PET films and fibers by alkoxysilane were then crosslinked by immersion of the samples in hot water. The crosslinking density was characterized by measuring the insoluble fraction of PET in good solvent constituted by a mixture of trifluoroacetic acid and dichloromethane (50/50 vol.). An insoluble fraction close to 70% was obtained by the functionalization treatment of amorphous PET film (8% crystallinity) by a mixture of GOPTMSI + IPTESI (50/50 M) at 155 °C for 1 h followed by hydrolysis-condensation reactions at 80 °C for 72 h. Thermomechanical and thermal properties of films and fibers were observed and found to be considerably enhanced in comparison to the untreated samples. The tensile properties of these partially crosslinked samples were maintained up to 320 °C.     

Effect of initiating groups introduced onto ultrafine silica on the molecular weight polystyrene grafted onto the surface

Summary The effect of initiating groups introduced onto silica surface on the molecular weight of grafted polystyrene chain was investigated. By the treatment of polystyrene-grafted silica with aqueous solution of alkali, surface grafted polystyrene was isolated from the surface. The molecular weight of polystyrene grafted onto the silica obtained from the radical graft polymerization initiated by peroxyester groups introduced onto the surface was found to be much larger than that from the cationic polymerization initiated by acylium perchlorate groups. The number of grafted polystyrene in the radical polymerization, however, was much less than that in the cationic polymerization. Furthermore, the effect of molecular weight of grafted polystyrene on the dispersibility of silica in tetrahydrofuran was examined.     

Thermally reversible crosslinked polyethylene using Diels–Alder reaction in molten state

Thermally reversible crosslinked polyethylene was prepared by Diels–Alder (DA) and retro Diels–Alder (rDA) reaction. Maleimide/furan adduct was used as crosslinking agent. Dienophile named 11-maleimido-undecanoic acid was first synthesized and between this dienophile and commercial 3-(2-furyl) propanoic acid, the DA reaction was studied to determine DA and rDA reactions temperatures in the solid state. Then, an original modification method was employed to graft the two molecules onto the Lotader® poly(ethylene-co-glycidyl methacrylate) in one step procedure. The DA and rDA reactions between diene and dienophile grafted moieties are followed by FT-IR analysis on a thin film. Readily polymer network is synthesized and the cycle of DA and retro-DA reactions is repeatable with no significant polymer degradation.     

Preparation and characterization of EVA–sisal fiber composites

In this work, composites of an EVA polymer matrix and short sisal fiber were characterized. The physical‐morphological as well as chemical interactions between EVA and sisal were investigated. When the samples were prepared in the presence of dicumyl peroxide, the results suggest that crosslinking of EVA as well as grafting between EVA and the sisal fibers took place. Morphological changes were studied by scanning electron microscopy (SEM). Results from Hg‐porosimetry, SEM, Fourier transform infrared spectroscopy, surface free energy, and gel content strongly indicate grafting of EVA onto sisal under the composite preparation conditions, even in the absence of peroxide. The grafting mechanism could not be confirmed from solid‐state ¹³C NMR analysis. The grafting had an impact on the thermal and mechanical properties of the composites, as determined by differential scanning calorimetry and tensile testing. Thermogravimetric analysis results show that the composites are more stable than both EVA and sisal fiber alone. The composite stability, however, decreases with increasing fiber content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1607–1617, 2006     

Grafting of branched polymers onto nano-sized silica surface: Postgrafting of polymers with pendant isocyanate groups of polymer chain grafted onto nano-sized silica surface

To control the surface wettability of nano-sized silica surface, the postgrafting of hydrophilic and hydrophobic polymers to grafted polymer chains on the surface was investigated. Polymers having blocked isocyanate groups were successfully grafted onto nano-sized silica surface by the graft copolymerization of methyl methacrylate (MMA) with 2-(O-[1′-methylpropylideneamino]caboxyamino)ethyl methacrylate (MOIB) initiated by azo groups previously introduced onto the surface. The blocked isocyanate groups of poly(MMA-co-MOIB)-grafted silica were stable in a desiccator, but isocyanate groups were readily regenerated by heating at 150 °C. The hydrophilic polymers, such as poly(ethylene glycol) (PEG) and poly(ethyleneimine) (PEI), were postgrafted onto the poly(MMA-co-MOIB)-grafted silica by the reaction of functional groups of PEG and PEI with pendant isocyanate groups of poly(MMA-co-MOI)-grafted silica to give branched polymer-grafted silica. The percentage of grafting increased with increasing molecular weight of PEG, but the number of postgrafted chain decreased, because of steric hindrance. The hydrophobic polymers, such as poly(dimethylsiloxane) were also postgrafted onto poly(MMA-co-MOI)-grafted silica. It was found that the grafting of hydrophobic polymer and the postgrafting of hydrophilic polymer branches readily controls the wettability of silica surface to water.     

Non-linear viscoelastic behaviour and modulus recovery in silica filled polymers

The viscoelastic properties of different silica filled polymers were investigated. A variety of rheological observations was studied in the molten state, such as Payne effect and modulus recovery kinetics, in ethylene vinyl acetate, polystyrene and polypropylene filled with non-porous silica. The concept of the filler network breakdown seems to be adequate in describing the strain-dependence of dynamic mechanical properties of composites. Recovery tests of the complex shear modulus performed by subsequent strain sweep or time sweep experiments show evidence that the initial equilibrium network structure cannot completely restore within several hours. Furthermore, new strain sweep experiment after in situ crystallisation (or glass transition in polystyrene composites) of the sample leads to a total recovery of the linear modulus suggesting that the silica network structure in molten state have the memory of the silica structure in solid state. On the other hand, the complex shear modulus measured at lower strain for cross-linked EVA composites are perfectly recoverable in few seconds as proven by subsequent strain sweeps.     

Morphology and properties of PBT/nylon 6/EVA‐g‐MAH ternary blends prepared by reactive extrusion

Morphology and properties of poly(butylene terephthalate) (PBT)/nylon 6 (PA6)/EVA‐g‐MAH ternary blends were investigated. The blends were prepared in a corotating, intermeshing, twin‐screw extruder. The incorporation of maleic anhyride (MAH) grafted onto ethylene‐vinyl acetate copolymer (EVA) (EVA‐g‐MAH) in the PBT/PA6 binary blends decreased the tensile and flexural strength but increased the impact strength, while the mechanical properties of the PBT/PA6 blends were decreased with increasing PA6 content regardless of the presence or absence of the EVA‐g‐MAH. The morphology studies of the ternary blends showed gross phase separation. The rheological properties of the ternary blends suggested that excessively high reactivity between amine end groups of PA6 and MAH grafted onto EVA makes the compatibility between PBT and PA6 worse, although EVA‐g‐MAH was expected to work as a compatibilizer for PBT/PA6 blends. The degree of reactivity between functional groups in PBT, PA6, and EVA‐g‐MAH was also examined by investigating the effect of blending sequence on the properties of the ternary blends.     

A FTIR study of interfacial interactions between ethylene copolymers and hydrated aluminium surfaces

Interfacial interactions to hydrated aluminium were examined for poly(ethylene-co-vinylacetate) EVA, poly(ethylene-co-butylacrylate) EBA, and poly(ethylene-co-acrylic acid) EAA. By means of IR reflection-absorption spectroscopy, the interactions between the effective functional groups were analysed at the polymer/aluminium interface. Thin copolymer films were prepared by solution casting onto aluminium, which had been hydrated by immersion in boiling water. The spectra representing the interface material revealed a strong hydrogen bond interaction between hydroxyl groups on the hydrated aluminium surface and the carbonyl oxygen in the ester group in EVA and EBA. The absorbance mode of the hydrogen bonded carbonyl was displaced to lower wavenumbers and appeared 34 cm^-1 and 38 cm^-1 below the 'free' carbonyl for EVA and EBA, respectively, which indicates that the hydrogen bond is very strong. For the C-O stretching mode in the ester group, a displacement of 36 cm ¹ in the opposite direction was observed, also an effect due to the hydrogen bond to the carbonyl. Furthermore, it was found that the absorptivity for the hydrogen bonded carbonyl was much higher than for the 'free', and for that reason a relative absorptivity ratio between them was determined. For EAA cast onto hydrated aluminium surfaces, the absorbance mode of the carbonyl disappeared, but new peaks arose at lower wavenumbers indicative of a carboxylate. This was explained to be due to a reaction between carboxylic acid groups and aluminium hydroxyl groups on the hydrated surface.     

Synthesis and characterization of poly(methyl methacrylate)‐grafted silica microparticles

A procedure to synthesize poly(methyl methacrylate)‐grafted silica microparticles was developed by using radical photopolymerization of methyl methacrylate (MMA) initiated from N,N‐diethyldithiocarbamate (DEDT) groups previously bound to the silica surface (grafting “from”). The functionalization of silica microparticles with DEDT groups was performed in two steps: introduction of chlorinated functions onto the surface of silica particles, and then nucleophilic substitution of chlorines by DEDT functions via a S_N2 mechanism. The study was performed with a Kieselgel® S silica which was initially chlorinated in surface, either by direct chlorination of silanols with thionyl chloride, or by using a condensation reaction between silanols and a chlorofunctional trialkoxysilane reagent, 4‐(chloromethyl)phenyltrimethoxysilane and chloromethyltriethoxysilane, respectively. Three types of DEDT‐functionalized silica microparticles were prepared with a good control of the reactions, and then characterized by solid‐state ¹³C and ²⁹Si CP/MAS NMR. Their ability to initiate MMA photopolymerization was studied. The kinetics of MMA photopolymerization was followed by HPLC and ¹H‐NMR. Whatever the silica used the grafting progresses very slowly. On the other hand, the conversion of MMA in PMMA grafts is depending on the structure of the DEDT‐functionalized Kieselgel® S used. Poly(methyl methacrylate)‐grafted silica microparticles bearing high length grafts ( about 100) were synthesized. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Adsorption and desorption of calcium ions by temperature swing with copolymer of thermosensitive and chelating components grafted on porous ethylene vinyl acetate disk

A novel adsorbent composed of a copolymer of a thermosensitive component, N-isopropylacrylamide (NIPAM), and a chelating component, N-(4-vinyl)benzylethylenediamine (VBEDA), was developed, and the adsorption and desorption behaviors of Ca²⁺ ions were investigated. The copolymer of NIPAM and VBEDA was grafted onto the pore surfaces of a porous ethylene vinyl acetate (EVA) disk by a plasma-initiated polymerization method. The copolymerization ratios of VBEDA were 3 and 6 mol%. Although a hydrophilic component, VBEDA, was copolymerized with NIPAM, the transition temperature of the copolymer was almost the same as that of poly(NIPAM). The permeability through the polymer-grafted EVA disk strongly depended on the temperature. It was quite low below the transition temperature of the grafted polymer, and increased drastically when the temperature exceeded the transition temperature. The polymer-grafted EVA disk adsorbed Ca²⁺ ions at low temperatures and the adsorption amount decreased significantly when the temperature exceeded the transition temperature of the grafted polymer, and repeated adsorption and desorption by temperature swings were possible. Furthermore, it was suggested that one Ca²⁺ ion was captured by three VBEDA groups, and this multi-point coordination bond was destroyed by heating as a result of shrinkage of the grafted poly(NIPAM-co-VBEDA) chains, leading to desorption of Ca²⁺ ion.     

Preparation and characterization of end-alkoxysilylated polystrene and the grafting behaviors onto inorganic pigments. I. Utilization of 4-isopropoxydimethylsilyl-α-methylstyrene

Novel end-functional polystyrene having isopropoxydimethylsilyl (IPS) groups at the end part of the chain was prepared. IPS groups were introduced by the reaction between the living polystyryl anion and 4-isopropoxydimethylsilyl-α-methylstyrene ( 1 ) in THF at 195 K. The resultant polymer was characterized by GPC, ¹H-NMR, and TLC. It was confirmed that the polymer had several units of 1 at the chain end and a fairly narrow molecular weight distribution. IPS groups in the polymer can be hydrolyzed with strong acid such as mono-n-butylphosphate (MBP) but not with weak acid and base. Grafting behaviors of the polymer onto silica and alumina were studied in toluene in the presence of MBP as a catalyst. The polymer was grafted onto silica effectively. However, it cannot be grafted onto alumina because of predominant adsorption of MBP onto alumina having a basic surface. © 1995 John Wiley & Sons, Inc.     

Selective Solid Phase Extraction of Chromium(VI) using Silica Gel Immobilized 4-vinyl Pyridine/Cupric Ion Complex

Immobilization of 4-vinyl pyridine (4-VP) onto silica gel (SG) and its coordination with cupric ion (SG-4-VP→Cu²⁺) leading to a new solid phase extractor has been carried out by a simple chemical technique. Immobilization and coordination reactions are characterized by chemical, FTIR, UV, and thermo-gravimetric analysis. The role of cupric ion on Cr(VI) binding capacity of the synthesized organic-inorganic hybrid material has been elucidated. The silica gel immobilized 4-VP/Cu²⁺ complex (hybrid material) is tested for selective extraction and pre-concentration of Cr(VI) from aqueous solution. The Cr(VI) binding behavior of the synthesized material is studied at different pH, time, and temperature of the medium in both competitive and non-competitive conditions.     

Composites from furfuryl alcohol and inorganic solids by cationic initiation, 3. Scanning electron microscopic investigations of solid poly(furfuryl alcohol)-silica composites

Composites of poly(furfuryl alcohol) grafted onto silica, with different percentage of grafting, have been investigated by scanning electron microscopy, elemental analysis and UV/Vis-reflectance spectroscopy. The size of the silica particles used for the coating procedure is not changed till a percentage of grafting to around 30%. A content of polymer higher than 35 wt.-% enhances the bonding between the particles due to the crosslinking of poly(furfuryl alcohol) on the surface with those in solution leading to the agglomeration of the particles. A general model of cross-linked poly(furfuryl alcohol)-silica composites is suggested.     

Synthesis and properties of grafted latices from a soybean oil‐based waterborne polyurethane and acrylics

A novel soybean oil‐based vinyl‐containing waterborne polyurethane (VPU) dispersion has been successfully synthesized from toluene 2,4‐diisocyanate, dimethylol propionic acid and a 90 : 10 mixture of chlorinated soybean oil‐based polyol and acrylated epoxidized soybean oil (AESO). Then, a series of VPU/acrylic grafted latices have been prepared by emulsion graft copolymerization of acrylic monomers (40 wt % butyl acrylate and 60 wt % methyl methacrylate) in the presence of the VPU dispersion, using potassium persulfate as an initiator. The structure, morphology, and thermal and mechanical properties of the resulting latices, containing 15–60 wt % soybean oil‐based polyols as a renewable resource, have been investigated by Fourier transform infrared spectroscopy, solid state ¹³C NMR spectroscopy, transmission electron microscopy, thermogravimetric analysis, dynamic mechanical analysis, and mechanical testing. The results indicate that graft copolymerization of the acrylic monomers onto the VPU network occurs during emulsion polymerization, leading to a significant increase in the thermal stability and mechanical properties of the resulting miscible grafted latices. This work provides new environmentally‐friendly latices from a renewable resource with high performance for coating applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The preparation of multi-walled carbon nanotubes encapsulated by poly(3-acrylaminopropylsiloxane) with silica nanospheres on the polymer surface

A silica-polymer-carbon nanotube hybrid was prepared in which the nanotubes were encapsulated by poly(3-acrylaminopropylsiloxane) with silica nanospheres on the polymer surface. First, highly reactive poly(acryloyl chloride) (PAC) was grafted onto the nanotubes through the reaction of side acyl chloride groups with hydroxyl groups present on the surface of acid-oxidized nanotubes. Second, reacting 3-aminopropyltriethoxysilane with the grafted PAC through the reaction between amino and acyl chloride groups, siloxane-containing sub-grafts were introduced onto the primary PAC grafts. Third, silica nanospheres were covalently linked to the sub-grafts by condensation to form a nanotube-polymer-silica hybrid. Each intermediate structure was confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM). TEM observation revealed a nanostructure in which the nanotube was encapsulated with a polymer layer bearing silica nanospheres on its surface.     

Functional polymers supported on porous silica. II.Radical polymerization of vinylbenzyl chloride from grafted precursors

Vinylbenzyl chloride was chosen as a model monomer for grafting a functional polymer onto silica carrying radical active precursors, such as monomer, transfer agent or initiator, previously grafted onto silica via a suitable coupling agent. The grafting efficiency was studied as a function of the texture of the initial silica, the nature of the active precursor and the polymerization conditions. Evidence for grafting was obtained from FTIR and ²⁹Si CP-MAS NMR spectra, and the thickness of the grafted layer was estimated from surface area and porosimetry measurements. From molecular weight measurements of nongrafted polymer it can be deduced that there is a trend toward the elongated conformation of the grafted polymer. Attempts to separate the grafted polymer through digestion of the silica with HF, failed to give a soluble linear polymer except when the active precursor was a transfer agent; in the two other cases a crosslinked polymer with a low crosslink density was obtained, which kept the morphology of the initial silica.     

Tailoring mechanical properties of highly porous polymer foams: Silica particle reinforced polymer foams via emulsion templating

The aim of this work was to synthesise highly open porous low-density polymer foams with superior mechanical properties by the polymerisation of the organic phase of concentrated emulsions. The continuous organic phase of the concentrated emulsion template occupying up to 40 vol% was polymerised leading to polymer foams with much improved mechanical properties. The Young's modulus as well as the crush strength of the foams was further increased dramatically by reinforcing the polymer phase with nanosized silica particles. To ensure that the silica particles were covalently incorporated into the polymer network, methacryloxypropyltrimethoxysilane (MPS) was added to the formulation, which reacts with the silica via hydrolysis reactions. The Young's modulus of silica reinforced foams increased by 280% and the crush strength by 218% in comparison to foams without reinforcement.