Grafting Of Polystyrene Research Articles

Covalent attachment of polystyrene on multi-walled carbon nanotubes via nitroxide mediated polymerization

A new method to attach polymers on carbon nanotubes has been studied. We used nitroxide mediated polymerization (NMP) to graft polystyrene from multi-walled carbon nanotubes (MWNTs). Carboxyl groups on MWNTs were activated with thionyl chloride (SOCl2) to give acyl chloride derivative (MWNT-COCl). NMP initiator was introduced to MWNT by esterification of 1-hydroxy-2-phenyl-2-(2′,2′, 6′, 6′-tetramethyl-1′-piperidinyloxy)ethane (HO-PE-TEMPO) with acyl chloride groups of MWNTs. The obtained MWNT-PE-TEMPO was used for initiation of bulk polymerization of styrene, yielding polystyrene-grafted MWNTs (MWNT-g-pSt). The resulting composites of MWNT-g-pSt were analyzed by TEM, SEM, FT-IR and TGA.

Preparation of poly(styrene‐co‐acrylonitrile)‐grafted multiwalled carbon nanotubes via surface‐initiated atom transfer radical polymerization

AbstractThe in situ grafting‐from approach via atom transfer radical polymerization was successfully applied to polystyrene, poly(styrene‐co‐acrylonitrile), and polyacrylonitrile grafted onto the convex surfaces of multiwalled carbon nanotubes (MWCNTs) with (2‐hydroxyethyl 2‐bromoisobutyrate) as an initiator. Thermogravimetric analysis showed that effective functionalization was achieved with the grafting approach. The grafted polymers on the MWCNT surface were characterized and confirmed with Fourier transform infrared spectroscopy and nuclear magnetic resonance. Raman and near‐infrared spectroscopy revealed that the grafting of polystyrene, poly(styrene‐co‐acrylonitrile), and polyacrylonitrile slightly affected the side‐wall structures. Field emission scanning electron microscopy showed that the carbon nanotube surface became rough because of the grafting of the polymers. Differential scanning calorimetry results indicated that the polymers grafted onto MWCNTs showed higher glass‐transition temperatures. The polymer‐grafted MWCNTs exhibited relatively good dispersibility in an organic solvent such as tetrahydrofuran. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 460–470, 2007

Synthesis of poly(vinyl acetate)‐graft‐polystyrene by a combination of cobalt‐mediated radical polymerization and atom transfer radical polymerization

AbstractVinyl acetate and vinyl chloroacetate were copolymerized in the presence of a bis(trifluoro‐2,4‐pentanedionato)cobalt(II) complex and 2,2′‐azobis(4‐methoxy‐2,4‐dimethylvaleronitrile) at 30 °C, forming a cobalt‐capped poly(vinyl acetate‐co‐vinyl chloroacetate). The addition of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy after a certain degree of copolymerization was reached afforded 2,2,6,6‐tetramethyl‐1‐piperidinyloxy‐terminated poly(vinyl acetate‐co‐vinyl chloroacetate) (PVOAc–MI; number‐average molecular weight = 31,000, weight‐average molecular weight/number‐average molecular weight = 1.24). A 1H NMR study of the resulting PVOAc–MI revealed quantitative terminal 2,2,6,6‐tetramethyl‐1‐piperidinyloxy functionality and the presence of 5.5 mol % vinyl chloroacetate in the copolymer. The atom transfer radical polymerization (ATRP) of styrene (St) was studied with ethyl chloroacetate as a model initiator and five different Cu‐based catalysts. Catalysts with bis(2‐pyridylmethyl)octadecylamine (BPMODA) or tris(2‐pyridylmethyl)amine (TPMA) ligands provided the highest initiation efficiency and best control over the polymerization of St. The grafting‐from ATRP of St from PVOAc–MI catalyzed by copper complexes with BPMODA or TPMA ligands provided poly(vinyl acetate)‐graft‐polystyrene copolymers with relatively high polydispersity (>1.5) because of intermolecular coupling between growing polystyrene (PSt) grafts. After the hydrolysis of the graft copolymers, the cleaved PSt side chains had a monomodal molecular weight distribution with some tailing toward the lower number‐average molecular weight region because of termination. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 447–459, 2007

Polymer Brush Grafted from an Allylsilane-Functionalized Surface

To graft polymer chains from the surface, a uniform and dense initiator layer on the silicate substrate is indispensable. The initiator monolayer can be fabricated in many ways, of which self-assembly of trichlorosilanes on silicate substrates is widely used. However, uniformity is always going to be an issue when using multifunctional silanes. Although uniformity is not so problematic for monofunctional silanes, purification of the surface-active materials is difficult. To obtain a uniform initiator monolayer, an allylsilane was synthesized and used to functionalize a flat silicate substrate in this research. The allylsilane can also be purified using conventional chromatography techniques. Using AFM, the monolayer was found to be more uniform than the corresponding trichlorosilane-functionalized one. Finally, atom transfer radical polymerization was applied to graft polystyrene brushes. The ability to successfully perform sequential monomer additions was consistent with a living polymerization. Tensiome...

Synthesis of Substituted Polyacetylenes Grafted with Polystyrene Chains by the Macromonomer Method and Their Characterization

Summary: A macromonomer (1) consisting of a polystyrene chain and an acetylenic chain end ( = 2 500, = 1.20) was prepared by atom transfer radical polymerization. Macromonomer 1 was copolymerized with phenylacetylene (2) and propargyl 2-bromopropionate (3) by using Rh catalysts at varying feed ratios from 10 to 50 wt.-% to produce graft copolymers 4 and 5, respectively. The synthesized copolymers 4 and 5 possessed a conjugated polyene main-chain and polystyrene grafts, and contained 11–34 and 16–77 wt.-% of polystyrene with of 61 400–144 000 and 19 300–22 500, respectively. Graft copolymer 4 was a yellow solid and thermally stable up to 225 °C, whereas 5 was a brown solid with weight loss beginning at 175 °C. Graft copolymers 4 and 5 exhibited UV-vis absorption edges at 525 and 425 nm, respectively, which are attributable to the conjugated main-chain structure. Copolymerization of the acetylene-terminated polystyrene-based macromonomer with monosubstituted acetylenes.

Graft Copolymers from Poly(vinylidene fluoride-co-chlorotrifluoroethylene) via Atom Transfer Radical Polymerization

We report the grafting of polystyrene (PS) and poly(tert-butyl acrylate) (PtBA) from poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) via atom transfer radical polymerization (ATRP). The initiating sites on P(VDF-co-CTFE) for the graft copolymerization are the secondary chlorines, indicated by the model reactions using poly(chlorotrifluoroethylene) (PCTFE) oligomer and the control experiment using poly(vinylidene fluoride) (PVDF). The formation of graft copolymers, P(VDF-co-CTFE)-g-PS and P(VDF-co-CTFE)-g-PtBA, was confirmed by 1H NMR, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and atomic force microscopy (AFM) measurements. The hydrolysis of PtBA grafts in P(VDF-co-CTFE)-g-PtBA resulted in amphiphilic graft copolymers with hydrophilic poly(acrylic acid) (PAA) side chains. The synthetic approach reported here offers a convenient way to modify commercial fluoropolymers containing CTFE units. The resultant graft copolymers may find potential applications such as materials for filtration membranes.

Surface properties of block and graft polystyrene–polydimethylsiloxane copolymers

AbstractThe surface compositions of a series of polystyrene‐b‐polydimethylsiloxane (PS‐b‐PDMS) and polystyrene‐g‐polydimethylsiloxane (PS‐g‐PDMS) copolymers were investigated using ATR‐FTIR and XPS technique. The results showed that enrichment of PDMS soft segments occurred on the surface of the block copolymers as well as on that of graft copolymers. And the magnitude order of the enrichment was as follows: PS‐b‐PDMS > PS‐g‐PDMS, which was attributed to the facilitating of the movement of the PDMS segments in PS‐b‐PDMS copolymer. Meanwhile, the solvent type and the contact medium had influence on the accumulation of PDMS on the surfaces. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

Design of new styrene enriched polyethylenes via coordination copolymerization of ethylene with mono- or α,ω-difunctional polystyrene macromonomers

ω-Allyl, ω-undecenyl and α,ω-undecenyl polystyrene macromonomers, well defined in molar mass and functionality, were synthesized via anionic polymerization. Their coordination copolymerization with ethylene with a cationic α-diimine palladium catalyst [ ( ArN = C ( Me ) – C ( Me ) = NAr ) Pd ( CH 2 ) 3 ( COOMe ) ] + BAr 4 ′ − , (Ar=2,6- iPr 2–C 6H 3 and Ar′=3,5-(CF 3) 2–C 6H 3) affords access to a new type of graft copolymers constituted of a polyethylene backbone and polystyrene grafts. It was shown that the environment of the terminal double bond of the PS macromonomers has a huge influence on the polymerization behavior. Indeed, an undecenyl end-group is more reactive than an allyl end-group. The copolymerization of ethylene with α,ω-undecenyl polystyrene macromonomers lead to cross-linking for long polymerization time (18 h at 25 °C). The influence of several parameters (polymerization temperature, ethylene pressure, concentration) on molar masses and macromonomer incorporation yield was also investigated. Macromonomers having the lowest molar masses were the most reactive. The molar mass of the copolymer increased with ethylene pressure. As expected with such a chain walking catalyst, the copolymers presented moderately branched to highly branched structures depending on the ethylene pressure, like for the homopolymerization of ethylene. Finally, rheological investigations of the copolymers showed that a few percentage of polystyrene incorporation can change drastically the mechanical properties of the materials.

Macromolecular anchoring layers for polymer grafting: comparative study

Comparative study of efficiency of macromolecular anchoring layers in the grafting of end-functionalized polymers to a surface was conducted. Poly(glycidyl methacrylate) (PGMA) and epoxydized polybutadienes (EPB) were utilized as the primary anchoring films. Amount of the epoxy moieties introduced to the surface was varied via thickness of the modifying polymer layer or amount of epoxy groups in the polymer backbone. Comparison between the grafting of polystyrene and poly(ethylene glycol) to the various macromolecular anchoring layers indicated that grafting ability of a layer was mostly governed by thickness of the interpenetration zone between the two polymers (anchoring and being grafted). In case of low level of the interpenetration, only functional groups at the periphery of the primary polymer layer were available for the grafting. Then, amount of grafted polymer did not increase with total number of epoxy groups in the anchoring film. However, as the thickness of the interpenetration zone increased, higher amount of the functional groups become available for the grafting.

Nafion ®- graft-polystyrene sulfonic acid membranes for direct methanol fuel cells

Polystyrene (PS) molecules were grafted onto the surface of a Nafion ® 117 membrane via the plasma-induced polymerization technique in order to reduce its methanol permeability in applications involving direct methanol fuel cells (DMFCs). The PS grafting reaction and degree of sulfonation were measured using FT-IR–ATR spectroscopy and XPS, respectively. The kinetics and equilibrium yield of the grafting reaction were analyzed by measuring the changes in the weight and thickness of the membranes during the grafting reactions. Crosslinking affected not only the grafting rate, but also the size and distribution of the ionic clusters in the membrane in the water swollen state. The equilibrium water uptake, proton conductivity and methanol permeability were affected by both the extent of the grafting reaction and the crosslinking density. The crosslinked polystyrene sulfonic acid (PSSA) layers that were grafted reduced the methanol permeability of the membranes considerably.

Rheological properties of branched polystyrenes: linear viscoelastic behavior

Oscillatory shear measurements on a series of branched graft polystyrenes (PS) synthesized by the macromonomer technique are presented. The graft PS have similar molar masses (Mw between 1.3×105 g/mol and 2.4×105 g/mol) and a polydispersity Mw/Mn around 2. The molar masses of the grafted side chains Mw,br range from 6.8×103 g/mol to 5.8×104 g/mol, which are well below and above the critical entanglement molar mass Mc of linear polystyrene. The average number \({\ifmmode\expandafter\bar\else\expandafter\fi{p}}\) of side chains per molecule ranges from 0.6 to 6.7. The oscillatory measurements follow the time–temperature superposition principle. The shift factors do not depend on the number of branches. The zero-shear viscosities of all graft PS are lower than those of linear PS with the same molar mass, which can be attributed to the smaller coil size of the branched molecules. It is shown that the influence of branching on the frequency dependence of the dynamic moduli is weak for all graft PS that were investigated, which can be explained by the low entanglement density.

Rheological properties of branched polystyrenes: linear viscoelastic behavior

Oscillatory shear measurements on a series of branched graft polystyrenes (PS) synthesized by the macromonomer technique are presented. The graft PS have similar molar masses (M w between 1.3×105 g/mol and 2.4×105 g/mol) and a polydispersity M w /M n around 2. The molar masses of the grafted side chains M w,br range from 6.8×103 g/mol to 5.8×104 g/mol, which are well below and above the critical entanglement molar mass M c of linear polystyrene. The average number \({\ifmmode\expandafter\bar\else\expandafter\fi{p}}\) of side chains per molecule ranges from 0.6 to 6.7. The oscillatory measurements follow the time–temperature superposition principle. The shift factors do not depend on the number of branches. The zero-shear viscosities of all graft PS are lower than those of linear PS with the same molar mass, which can be attributed to the smaller coil size of the branched molecules. It is shown that the influence of branching on the frequency dependence of the dynamic moduli is weak for all graft PS that were investigated, which can be explained by the low entanglement density.

Polymerizable Living Free Radical Initiators as a Platform To Synthesize Functional Networks

Photopolymerizations of multifunctional monomers afford spatial and temporal control of cross-linked network formation whereas living radical polymerizations provide a means to synthesize well-defined architectures from monovinyl monomers. By combination of these technologies in a two-stage polymerization process, a novel method is developed to synthesize functional polymer networks, and supporting results are provided for preparing controlled polymer grafts within photo-cross-linked networks. To demonstrate the concept of internal grafting, an alkoxyamine living radical initiator (for nitroxide-mediated polymerization, NMP) and a tertiary bromide initiator (for atom-transfer radical polymerization, ATRP) were functionalized with a methacrylate group and either was copolymerized with mono- and divinyl methacrylic monomers during the initial network formation step. Activation of the living radical initiators within styrene-swollen networks resulted in controlled molecular weight polystyrene grafts covalently bound to the photo-cross-linked methacrylic networks. To demonstrate the applicability of this technology for synthesizing functional networks, hydrogels with nitroxide groups were first photopolymerized, and different concentrations of acetoacetoxy, (i.e., ketoester) functionality were subsequently grafted within the loosely cross-linked networks. When the grafted networks were swollen in aqueous solutions containing Fe3+, the cations coordinated with the grafted ketoester moieties. In general, this robust technology could be applied to a wide array of monomers and functional groups to control the chemical, physical, and mechanical properties of the final grafted network for application in sensors, catalysis, separations, and combinatorial chemistry platforms.

Surface studies of radiation grafted sulfonic acid membranes: XPS and SEM analysis

PTFE-g-polystyrene sulfonic acid membranes prepared by radiation-induced graft copolymerization of styrene onto poly(tetrafluoroethylene) (PTFE) films followed by sulfonation reactions were investigated with respect to their morphology and surface chemical properties. The chemical composition of the membranes surfaces was monitored at various degrees of grafting using X-ray photoelectron spectroscopy (XPS). Considerable differences in the concentration of the chemical components of the surfaces were observed despite the predominance of all membranes surfaces by a hydrocarbon fraction originated from the incorporated sulfonated polystyrene grafts. The distribution of the sulfonated polystyrene grafts in membranes having various degrees of grafting was investigated by scanning electron microscopy (SEM). The membranes achieved a homogenous distribution at degrees of grafting of 24% and above. The results of this work suggest that the membranes have a chemically sensitive surfaces and this is most likely to have an impact on their interfacial properties and chemical stability.

Synthesis of syndiotactic-polystyrene- graft-poly(methyl methacrylate) and syndiotactic-polystyrene- graft-atactic-polystyrene by atom transfer radical polymerization

Syndiotactic polystyrene graft copolymers, including syndiotactic-polystyrene- graft-poly(methyl methacrylate) and syndiotactic-polystyrene- graft-atactic-polystyrene, were synthesized by atom transfer radical polymerization (ATRP) using bromoacetylated syndiotactic polystyrene as macroinitiator and copper bromide combined with 2,2′-bipyridine as catalyst. The macroinitiator was prepared from the acid-catalyzed halogenation reaction of partially acetylated syndiotactic polystyrene, which was synthesized in a heterogeneous process with acetyl chloride and anhydrous aluminum chloride in carbon disulfide. The graft copolymers were characterized by 1H- and 13C-NMR spectra.

Physico-chemical study of sulfonated polystyrene pore-filled electrolyte membranes by electrons induced grafting

Pore-filled polymer electrolyte membranes have been prepared as a potential proton exchange membrane by radiation induced grafting using simultaneous technique. The porous substrate films were grafted in a subsequent step after flooding the membranes pores with styrene monomer. The grafted films were then sulfonated in a post-grafting reactions. The influence of grafting conditions, i.e. irradiation dose and monomer concentration in correlation with the grafting yield ( Y) have been investigated. The results showed that the grafting yield is increased for both conditions. The resulting membranes were then characterized by evaluating their physico-chemical properties such as ion exchange capacity, water uptake and proton conductivity as a function of grafting yield. The overall results showed that polystyrene grafts is successfully anchored within the pores of PTFE films during grafting and subsequently transformed into hygroscopic proton exchange regions after being sulfonated. The measured conductivity of the sulfonated polystyrene pore-filled electrolyte PTFE membranes achieved were approximately within the magnitude of 10 −3 and 10 −2 S cm −1 at room temperature and at higher operating temperature, respectively.

Properties of polyurethane–polystyrene graft copolymer membranes used for separating water–ethanol mixtures

Polyurethane prepolymers (PU) based on hydrophilic poly(ethylene glycol) (PEG), hydroxypropyl acrylic acid (HPA), 2,4-toluene diisocyanate (TDI), and butanediol (BDO) were prepared by one-step polymerization with butanediol as the chain extender. Polyurethane–polystyrene graft copolymers (PU-g-PS) were synthesized by free radical copolymerization of PU with styrene (ST), 2,2′-azobisisobutyronitrile (AIBN) was used as initiator and toluene as solvent. Experimental results showed that the crosslinked membranes of PU–PS graft copolymers could be used for separating ethanol–water mixtures. The highest value of the separation factor ( α) of the crosslinked separation membranes can reach 17.3. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to characterize the properties of PU–PS crosslinked membranes.

Controlling the Number of Arms of Polymer Stars with a Fullerene C60 Core

Pure di‐ and tetra‐adducts can be obtained by grafting polystyrene (PS) chains onto C60 via an atom transfer radical addition. Stars with a C60 core and exactly six PS arms of molar mass ranging from 1000 to several 100,000 are easily produced by adding an excess of PSLi to the fullerene. Tri‐ to penta‐adducts can be prepared by controlling the stoichiometry PSLi/C60. The number of grafts on the fullerene can be extended to seven or eight by initiation of the anionic polymerization of an adequate monomer with a “living” hexa‐adduct or by grafting onto this latter an halogen terminated polymer.

Plasma induced grafting of PSt onto titanium dioxide powder. II

Grafting of polystyrene (PSt) onto titanium dioxide powder was investigated in this study. The graft polymerization reaction was induced by N2 plasma treatment of the surfaces of the titanium dioxide powder. IR and XPS results showed that PSt was grafted onto the titanium dioxide powder. The crystal structure of the titanium dioxide powder observed by XRD spectra was unchanged after plasma graft polymerization. In the grafting reaction, the grafting yield increased with the plasma power, the plasma treatment time, and the grafting reaction, but it increased first then decreased after reaching 50°C. The type of monomers also has an effect on the grafting yield. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2112–2117, 2005

Development and characterization of a microfiltration membrane catalyst containing sulfonated polystyrene grafts

Polymeric catalytic membrane reactors (CMRs) containing sulfonated polystyrene grafts can serve as an alternative to traditional strong acid catalysts such as sulfuric acid and strong acid ion-exchange resins (IERs) for esterification and alkylation reactions. This material offers advantages over conventional catalysts in terms of corrosivity, attrition, pressure drop, mass transfer limitations, and catalyst separation. The membrane reactors are functionalized membranes created by cationic polymerization of styrene in the pores of a porous matrix of polyethersulfone (PES). Sulfonation of the formed polystyrene grafts with sulfuric acid creates easily accessible sulfonic acid groups (∼2 meq/g) for catalysis. Diffusional limitations encountered in ion-exchange resins are minimized because transport through the membrane pore takes place by convection. Consequently, the membrane activation is accomplished with lower concentration acid. The activated membrane shows no loss of functionalized polymer during activation, demonstrating excellent material stability. Finally, the catalytic activity was verified for a simple esterification reaction between acetic acid and ethanol.