Effective grafting of polymers onto ultrafine silica surface: Photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface and Mn2(CO)10

The effective grafting of vinyl polymers onto an ultrafine silica surface was successfully achieved by the photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface with Mn₂(CO)₁₀ under UV irradiation at 25 °C. The introduction of trichloroacetyl groups onto the surface of silica was achieved by the reaction of trichloroacetyl isocyanate with surface amino groups, which were introduced by the treatment of silica with 3‐aminopropyltriethoxysilane. During the polymerization, the corresponding polymers were effectively grafted onto the surface, based on the propagation of polymer from surface radicals formed by the interaction of trichloroacetyl groups and Mn₂(CO)₁₀. The percentage of poly(methyl methacrylate) grafting onto the silica reached 714.6% after 90 min. The grafting efficiency (proportion of grafted polymer to total polymer formed) in the polymerization of methyl methacrylate was very high, about 80%, indicating the depression of formation of ungrafted polymer. Polymer‐grafted silica gave a stable colloidal dispersion in good solvents for grafted polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2157–2163, 2001     

Living cationic polymerization of isobutyl vinyl ether by the carboxyl group of the carbon black/zinc chloride initiating system

The effect of zinc chloride (ZnCl₂) on the cationic polymerization of isobutyl vinyl ether (IBVE) initiated by carboxyl groups on a carbon black surface was investigated. Although the polymerization of IBVE was initiated by carboxyl groups on the surface, the rate of polymerization was small and the molecular weight distribution (MWD) of poly IBVE was very broad. The rate of the polymerization was found to be drastically increased, and 100% monomer conversion was achieved in a short time by the addition of ZnCl₂. The number-average molecular weights (M_n) of the polyIBVE were directly proportional to monomer conversion in the polymerization initiated by the carbon black/ZnCl₂ system. By addition of the monomer at the end of the first-stage polymerization, the added monomer was smoothly polymerized at the same rate as in the first stage. The M_n of the polymer was in excellent agreement with the calculated value, assuming the polyIBVE chain forms per unit carboxyl group on the surface and MWD was narrow (M_w/M_n = 1.2 ～ 1.3). Based on the results, it is concluded that carbon black/ZnCl₂ system has an ability to initiate the living cationic polymerization of IBVE. Furthermore, it was found that polyIBVE was grafted onto the carbon black surface after the quenching of the living polymer with methanol. © 1995 John Wiley & Sons, Inc.     

Polymer grafting onto carbon black by use of TEMPO-terminated polystyrene with controlled molecular weight

The grafting of polystyrene with controlled molecular weight and narrow molecular weight distribution onto the carbon black surface through the trapping of polymer radicals formed by the thermal dissociation of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-terminated polystyrene (PSt-TEMPO) by the carbon black surface was investigated. PSt-TEMPO was prepared by living radical polymerization of St with the benzoyl peroxide/TEMPO system. When PSt having no terminal TEMPO moiety was heated with carbon black, no grafting of PSt onto the surface was observed. On the contrary, by the heating of PSt-TEMPO with carbon black in m-xylene at 125°C, PSt with controlled molecular weight and narrow molecular weight distribution was grafted onto the surface: the percentage grafting of PSt (M_n = 3.2 × 10³;M_w/M_n = 1.07) onto furnace black was determined to be 16.0%. On the basis of the above results, it is concluded that PSt radicals formed by the thermal dissociation of the C ON bond between PSt and TEMPO are trapped by polycondensed aromatic rings of carbon black. The mole number of grafted PSt chains on the carbon black surface decreased with increasing molecular weight of PSt-TEMPO. PSt-grafted carbon black gave a stable colloidal dispersion in THF. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3165–3172, 1998     

Synthesis of well-defined, polymer-grafted silica nanoparticles via reverse ATRP

The surface grafting onto ultrafine silica via reverse ATRP of methyl methacrylate initiated by peroxide groups introduced onto the surface and conventional ATRP of Styrene initiated by the hybrid nanoparticles were investigated. The introduction of peroxide groups onto the silica surface was achieved by the reaction of hydrogen peroxide with chlorosilyl groups, which were introduced by the treatment of silica with thionyl chloride. Well-defined polymer chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined, densely grafted outer polymer layer. The polymerization was closely controlled in solution at quite low temperature such as 70 °C. In both cases, linear kinetic plots, linear plots of molecular weight (M_n) versus conversion, in hydrodynamic diameter with increasing conversion, and narrow molecular weight distributions (M_w/M_n) for the grafted polymer samples were observed. Hydrolysis of silica cores by hydrofluoric acid treatment enabled characterization of cleaved polymer using GPC. Ultrathin films of hybrid nanoparticles were examined using TEM and AFM.     

Grafting of polymers onto and/or from silica surface during the polymerization of vinyl monomers in the presence of γ‐ray‐irradiated silica

The effects of radicals on silica surface, which were formed by γ‐ray irradiation, on the polymerization of vinyl monomers were investigated. It was found that the polymerization of styrene was remarkably retarded in the presence of γ‐ray‐irradiated silica above 60 °C, at which thermal polymerization of styrene is readily initiated. During the polymerization, a part of polystyrene formed was grafted onto the silica surface but percentage of grafting was very small. On the other hand, no retardation of the polymerization of styrene was observed in the presence of γ‐ray‐irradiated silica below 50 °C; the polymerization tends to accelerate and polystyrene was grafted onto the silica surface. Poly(vinyl acetate) and poly(methyl methacrylate) (MMA) were also grafted onto the surface during the polymerization in the presence of γ‐ray‐irradiated silica. The grafting of polymers onto the silica surface was confirmed by thermal decomposition GC‐MS. It was considered that at lower temperature, the grafting based on the propagation of polystyrene from surface radical (“grafting from” mechanism) preferentially proceeded. On the contrary, at higher temperature, the coupling reaction of propagating polymer radicals with surface radicals (“grafting onto” mechanism) proceeded to give relatively higher molecular weight polymer‐grafted silica. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2972–2979, 2006     

Photografting of polymers onto nanosized silica surface initiated by eosin moieties immobilized onto the surface

The photograft polymerization of various vinyl monomers onto nanosized silica surfaces was investigated. It was initiated by eosin moieties introduced onto the silica surface. The preparation of the silica with eosin moieties was achieved by the reaction of eosin with benzyl chloride groups on the silica surface.These were introduced by the reaction of surface silanol groups with 4‐(chloromethyl)phenyltrimethoxysilane in the presence of t‐butyl ammonium bromide as a phase‐transfer catalyst. The photopolymerization of various vinyl monomers, such as styrene, acrylamide, acrylic acid, and acrylonitrile was successfully initiated by eosin moieties on the silica surface in the presence of ascorbic acid as a reducing agent and by oxygen. The corresponding polymers were grafted from the silica surface. The grafting efficiency (percentage of grafted polymer to total polymer formed) in the photoinitiation system was much larger than that in the radical polymerization initiated by surface radicals; these radicals were formed by the thermal decomposition of azo groups introduced onto the silica surface. It was found that the polymer‐grafted silica gave stable dispersions in good solvents of grafted polymer and the wettability of the surfaces can be easily controlled by grafting of polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 600–606, 2005     

Scale‐up synthesis of hyperbranched poly(amidoamine)‐grafted ultrafine silica using dendrimer synthesis methodology in solvent‐free dry‐system

Scale‐up synthesis of hyperbranched poly(amidoamine)‐grafted ultrafine silica was successfully achieved by using dendrimer synthesis methodology in solvent‐free dry‐system. The poly(amidoamine) was allowed to grow from silica surface by repeating two steps: (1) Michael addition of methyl acrylate (MA) to amino group on the surface and (2) amidation of terminal ester group with ethylenediamine (EDA). MA was sprayed onto silica having amino group and the silica agitated at 300 rpm at 50 °C. After the reaction, unreacted MA was removed under vacuum. Then EDA was sprayed and the reaction was conducted at 50 °C with agitation. After the reaction, unreacted EDA was also removed under vacuum at 50 °C and MA was sprayed again. The percentage of poly(amidoamine) grafting onto the surface was determined to be 141% with repeated reaction cycles of eight‐times. However, the value was considerably smaller than that of the theoretical value. This indicates that the propagation of poly(amidoamine) dendron from silica surface was not achieved theoretically and hyperbranched poly(amidoamine) was grafted onto the surface because of steric hindrance of grafted polymer. In addition, the effect of initial amino group content on the growth of poly(amidoamine) from the surface was investigated. It was concluded that the method is suitable for the scale‐up synthesis of hyperbranched poly(amidoamine)‐grafted silica. Copyright © 2002 John Wiley & Sons, Ltd.     

Surface grafting of polymers onto inorganic ultrafine particles: Reaction of functional polymers with acid anhydride groups introduced onto inorganic ultrafine particles

The surface grafting onto inorganic ultrafine particles, such as silica, titanium oxide, and ferrite, by the reaction of acid anhydride groups on the surfaces with functional polymers having hydroxyl and amino groups was examined. The introduction of acid anhydride groups onto inorganic ultrafine particle was achieved by the reaction of hydroxyl groups on these surfaces with 4-trimethoxysilyltetrahydrophthalic anhydride in toluene. The amount of acid anhydride groups introduced onto the surface of ultrafine silica, titanium oxide, and ferrite was determined to be 0.96, 0.47, and 0.31 mmol/g, respectively, by elemental analysis. Functional polymers having terminal hydroxyl or amino groups, such as diol-type poly(propylene glycol) (PPG), and diamine-type polydimethylsiloxane (SDA), reacted with acid anhydride groups on these ultrafine particles to give polymer-grafted ultrafine particles: PPG and SDA were considered to be grafted onto these surfaces with ester and amide bond, respectively. The percentage of grafting increased with increasing acid anhydride group content of the surface: the percentage of grafting of SDA (M_n = 3.9 × 10³) onto silica, titanium oxide, and ferrite reaching 64.7, 33.7, and 24.1%, respectively. These polymer-grafted ultrafine particles gave a stable colloidal dispersion in organic solvents.     

Photografting of vinyl polymers onto ultrafine inorganic particles: Photopolymerization of vinyl monomers initiated by AZO groups introduced onto these surfaces

The photografting of polymers onto ultrafine inorganic particles, such as silica and titanium oxide, initiated by azo groups introduced onto these surfaces was investigated. The introduction of azo groups onto the particles was achieved by the reaction of 4,4′-azobis(4-cyanopentanoic acid) with surface isocyanate groups, which were introduced by the treatment with tolylene 2,4-diisocyanate. It was found that the photopolymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and N-vinylcarbazole, is initiated by ultrafine particles having azo groups. The corresponding polymers were effectively grafted onto these surfaces through the propagation of the polymer from the surface radicals formed by the photodecomposition of the azo groups: e.g., the percentage of grafting of PMMA and polystyrene onto silica was reached to 112 and 176%, respectively. The percentage of grafting onto silica in the graft polymerization initiated by photodecomposition of surface azo groups was much larger than that initiated by thermal decomposition. Polymer-grafted ultrafine particles thus obtained gave a stable colloidal dispersion in good solvents for the grafted chain. © 1994 John Wiley & Sons, Inc.     

Polymerization of vinyl monomers in the presence of silica having surface functional groups

The surface of silica was modified by mercaptopropyl, chloropropyl, aminopropyl, and methacryloxypropyl groups by the treatment of silica with the corresponding silane coupling agents, and the effects of functional groups on the surface on the polymerization of vinyl monomers initiated by benzoyl peroxide or 2,2-azobisisobutyronitrile were investigated. Although the rate of the polymerization of vinyl monomers in the presence of silica was almost equal to that in the absence of silica, a part of polymer formed was grafted onto silica surface. The polymerization was considerably retarded in the presence of these functionalized silicas and the corresponding polymers were effectively grafted onto the surface. The molecular weight of ungrafted polymer formed in the presence of the functionalized silica was lower than that formed in the presence of unmodified silica. This indicates that the chain transfer reaction of growing polymer radical to functionalized silica surface forms radicals on the surface, which then couples with growing polymer radical and/or reinitiates the polymerization to give rise to the grafting of polymers onto the surface. In the case of silica having methacryloxypropyl groups, the grafting based on the copolymerization of vinyl monomer with the surface methacryloxypropyl groups was considered to successfully proceed.     

“LIVING-LIKE” CATIONIC POLYMERIZATION OF ISOBUTYL VINYL ETHER INITIATED BY CARBOXYL GROUPS ON CARBON BLACK SURFACE/ETHYLALUMINUM DICHLORIDE SYSTEM IN THE PRESENCE OF 1,4-DIOXANE

The effect of 1,4-dioxane as an added base on the cationic polymerization of isobutyl vinyl ether (IBVE) initiated by carboxyl groups on carbon black surface/ethylaluminum dichloride (EtAlCl₂) system was investigated. Although the cationic polymerization of IBVE by carbon black/EtAlCl₂ system the absence of 1,4-dioxane instaneously proceeded and the monomer conversion achieved 100% within a minute. The molecular weight distribution (MWD) of polyIBVE obtained was very broad. On the contrary, the MWD of polyIBVE obtained was very narrow and narrower than that obtained from the carbon black/ZnCl₂ initiating system by the addition of 1,4-dioxane. The number-average molecular weight (Mn) of polyIBVE obtained was directly proportional to monomer conversion in the cationic polymerization. However, the Mn of polyIBVE obtained from the polymerization by the initiating system in the the presence of 1,4-dioxane was smaller than that of the calculated value, assuming that polyl(IBVE) chain forms per unit carboxyl group on carbon black surface. It was concluded that carbon black/EtAlCl₂ initiating systems in the presence of 1,4-dioxane has an ability to initiate “living-like” cationic polymerization of IBVE based on the above results. PolyIBVE was grafted onto a carbon black surface after quenching the above “living-like” cationic polymerization systems with methanol.     

Grafting of polymers onto a carbon‐fiber surface by ligand‐exchange reaction of poly(vinyl ferrocene‐co‐vinyl monomer) with polycondensed aromatic rings of the surface

To improve the surface of carbon fiber, the grafting reaction of copolymer containing vinyl ferrocene (VFE) onto a carbon‐fiber surface by a ligand‐exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of carbon fiber was investigated. The copolymer containing VFE was prepared by the radical copolymerization of VFE with vinyl monomers, such as methyl methacrylate (MMA) and styrene, using 2,2′‐azobisisobutyronitrile as an initiator. By heating the carbon fiber with poly(VFE‐co‐MMA) (number‐average molecular weight: 2.1 × 10⁴) in the presence of aluminum chloride and aluminum powder, the copolymer was grafted onto the surface. The percentage of grafting reached 46.1%. On the contrary, in the absence of aluminum chloride, no grafting of the copolymer was observed. Therefore, it is considered that the copolymer was grafted onto the carbon‐fiber surface by a ligand‐exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of carbon fiber. The molar number of grafted polymer chain on the carbon‐fiber surface decreased with increasing molecular weight of poly(VFE‐co‐MMA) because the steric hindrance of grafted copolymer on the carbon‐fiber surface increases with increasing molecular weight of poly(VFE‐co‐MMA). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1868–1875, 2002     

Preparation and properties of biocompatible polymer-grafted silica nanoparticle

Grafting of biocompatible polymer onto the surface of silica nanoparticles was achieved by radical graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC), initiated by azo groups previously introduced onto the surface or by a system consisting of Mo(CO)₆ and trichloroacetyl groups on the silica surface. Both of these systems have the ability to initiate graft polymerization of MPC, resulting in the formation of poly(MPC)-grafted silica, but the percentage of poly(MPC) grafting for the latter initiating system was much higher than that of the former. The amount of moisture that could be adsorbed onto the silica surface was found to increase with increasing poly(MPC) grafting. This indicates that grafting of poly(MPC) onto the silica surface markedly increases the hydrophilic nature of the surface. The contact angle of water in composites prepared from poly(vinyl alcohol) and poly(MPC)-grafted silica was found to decrease with increasing poly(MPC)-grafted silica content. When poly(MPC)-grafted silica was added to water containing a small amount of chloroform, it was found to act as stabilizer for droplets of chloroform. In addition, according to tests by the Lee-White method, poly(MPC)-grafted silica shows non-thrombogenic characteristics.     

Grafting onto carbon black by the reaction of reactive carbon black having masked isocyanate or acyl azide group with functional polymers

Although isocyanate group (NCO) introduced onto carbon black surface was inactivated rapidly upon storage, it could be stabilized by masking the NCO group with active hydrogen compounds such as acetylacetone, diethyl malonate, and sodium hydrogensulfite. Upon heating these carbon blacks having masked NCO group at 150°C, the NCO group was regenerated on carbon black by the decomposition of the masked NCO group. On the other hand, acyl azide (CON₃) group introduced onto carbon black was stable at below 20°C, but readily decomposed to NCO group by heating. By means of the reaction of NCO group on carbon black with functional polymers having hydroxyl, amino, and carboxyl group, these polymers were effectively grafted onto carbon black surface. When carbon black having CON₃ group was used as reactive carbon black, the grafting ratio of diol-type polyethylene glycol (M_n = 8.2 × 10³), polyethyleneimine (M_n = 2.0 × 10⁴), polyvinyl alcohol (M_n = 2.2 × 10⁴), and bifunctional carboxyl-terminated polystyrene (M_n = 1.1 × 10⁵) was determined to be 29.7, 81.7, 32.2, and 50.4%, respectively. The number of grafted polymer chain decreases with an increase in molecular weight of the polymers, because the shielding effect of NCO group by grafted polymer chain is enhanced with an increase in molecular weight of the polymer.     

Synthesis of well‐defined polymers end‐functionalized with crosslinkable aziridine groups by living anionic polymerization

Well‐defined end‐functionalized polystyrene, poly(α‐methylstyrene), and polyisoprene with polymerizable aziridine groups were synthesized by the termination reactions of the anionic living polymers of styrene, α‐methylstyrene, and isoprene with 1‐[2‐(4‐chlorobutoxy)ethyl]aziridine in tetrahydrofuran at ?78 °C. The resulting polymers possessed the predicted molecular weights and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.1) as well as aziridine terminal moieties. The cationic ring‐opening polymerization of the ω‐monofunctionalized polystyrene having an aziridinyl group with Et₃OBF₄ gave the polymacromonomer, whereas the α,ω‐difunctional polystyrene underwent crosslinking reactions to afford an insoluble gel. Crosslinking products were similarly obtained by the reaction of the α,ω‐diaziridinyl polystyrene with poly(acrylic acid)‐co‐poly(butyl acrylate). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4126–4135, 2005     

Surface Grafting onto Barium Sulfate: Polymerization of Acrylamide Initiated by the System Consisting of Alcoholic Hydroxyl Groups on the Surface and Ceric Ion

Abstract

To modify the surface of barium sulfate, the grafting of polymers onto the surface by the polymerization of acrylamide (AAm) initiated by the system consisting of eerie ion and alcoholic hydroxyl groups on the surface was investigated. Barium sulfate modified by 12-hydroxystearate (BaSO₄-HS) was prepared by the reaction of barium chloride with sodium sulfate containing a small amount of sodium 12-hydroxystearate. The presence of 12-hydroxystearate groups on the BaSO₄ surface was confirmed by XPS analysis and infrared spectra. It was found that the graft polymerization of AAm is initiated by the system consisting of eerie ion and BaSO₄-HS to give poly (AAm)-grafted BaSO₄. This indicated that the grafted polymer chains are propagated from surface radicals formed by the redox reaction of eerie ion with 12-hydroxystearate groups on the surface. The polymerization rate (R _p) of AAm initiated by the redox system was given by R _p = k[AAm][Ce(IV)][BaSO₄-HS] where k is constant, [AAm] is AAm concentration, [Ce(IV)] is cerie ion concentration, and [BaSO₄-HS] is BaSO₄-HS concentration. The result suggested that in such an initiating system, the unimolecular termination of growing polymer radicals from the surface of BaSO₄ proceeds preferentially. Furthermore, by grafting of poly(AAm) onto the BaSO₄-HS surface, the wettability of the surface was found to turn from hydrophobic to hydrophilic.     

Solvent replacement to thermo‐responsive nanoparticles from long‐subchain hyperbranched PSt grafted with PNIPAM for encapsulation

Long‐subchain hyperbranched polystyrene (lsc‐hp PSt) with uniform subchain length was obtained through copper‐catalyzed azide‐alkyne cycloaddition click chemistry from seesaw macromonomer of PSt having one alkynyl group anchored at the chain centre and two azido group attached to both chain ends [alkynyl‐(PSt‐N₃)₂]. After precipitation fraction, different portions of lsc‐hp PSt having narrow overall molecular weight distribution were obtained for further grafting with alkynyl‐capped poly(N‐isopropylacrylamide) (alkynyl‐PNIPAM), which was obtained via single‐electron transfer living radical polymerization of NIPAM with propargyl 2‐bromoisobutyrate as the initiator and grafted onto the peripheral azido groups of lsc‐hp PSt via click chemistry. Thus, amphiphilic lsc‐hp PSt grafted with PNIPAM chains (lsc‐hp PSt‐g‐PNIPAM) was obtained and would have star‐like conformation in tetrahydrofuran (THF). By replacing THF with water, lsc‐hp PSt‐g‐PNIPAM was dissolved at molecular level in aqueous solution due to the hydrophilicity of PNIPAM and exhibited thermal induced shrinkage of PNIPAM arms. The water‐insoluble lsc‐hp PSt would collapse densely and could be served as a reservoir to absorb hydrophobic chemicals in aqueous solution. The influence of overall molecular weight of lsc‐hp PSt on the absorption of pyrene was studied. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Grafting of hyperbranched poly(amidoamine) onto carbon black surfaces using dendrimer synthesis methodology

To modify carbon black surface, the surface grafting of hyperbranched poly(amidoamine) onto the surface by using dendrimer synthesis methodology was investigated. Carbon black having amino groups (initiator sites) was prepared by the reduction of surface nitro groups introduced by nitration of aromatic rings. It was found that hyperbranched poly(amidoamine) was propagated from carbon black surface by repeating two processes: (1) Michael addition of methyl acrylate (MA) to surface amino groups and (2) amidation of the resulting esters with ethylenediamine: the percentage of poly(amidoamine) grafting reached to 96.2% after 10th‐generation. The grafting of hyperbranched poly(amidoamine) onto polystyrene‐bead as a model compound of carbon black was also achieved by the above procedures. However, the theoretical propagation of poly(amidoamine) dendrimer was not achieved, because of steric hindrance of grafted polymer. Hyperbranched poly(amidoamine)‐grafted carbon black gave a stable dispersion in a good solvent for poly(amidoamine). Copyright © 2001 John Wiley & Sons, Ltd.     

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

The 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     

Surface-grafting onto aramid powder: reaction of acyl chloride groups on the surface with functional polymers having terminal hydroxyl or amino groups

The surface-grafting of polymers onto aramid, poly(p-phenylene terephthalamide), powder surface by the reaction of acyl chloride groups on the surface with functional polymers having terminal hydroxyl and amino groups was investigated. The introduction of acyl chloride groups onto the aramid powder surface was achieved by the reaction of the aramid powder with adipoyl dichloride: the acyl chloride group content of the surface was estimated to be 1.14 mmol/g (0.17 mmol/m²) by elemental analysis. It was found that by the reaction of acyl chloride groups on the surface with functional polymers, such as terminal diol-type poly(propylene oxide) (PPG) and terminal diamine-type poly(dimethylsiloxane) (SDA), these polymers were grafted onto the aramid powder surface; the percentage of surface grafting of PPG and SDA onto the aramid powder was 16.7 and 22.4%, respectively. The thermogravimetric curve of PPG surface-grafted aramid powder exhibited an initial weight loss at about 250°C and a second weight loss at about 500°C. This indicated that the grafting of PPG is limited to the powder surface. The wettability of the aramid powder surface turned from hydrophobic to hydrophilic by the surface-grafting of PPG onto the surface.