Graft copolymerization of methyl methacrylate onto curdlan

Graft copolymerization of methyl methacrylate onto curdlan was first investigated. In the graft copolymerization initiated by ammonium persulfate (APS) in DMSO under a homogeneous condition, the resulting graft copolymers had low molecular weights and low grafting percentages. However, the initiation by APS in water gave graft copolymers having relatively higher molecular weight ( ) and higher grafting percentage (548%) than those copolymers obtained by the homogeneous condition. When the graft copolymerization was carried out by cerium (IV) ammonium nitrate-HNO₃ initiation, the graft copolymer had the highest grafting percentage of 1620% without degradation of the curdlan backbone. The resulting graft copolymers were soluble in DMSO. The graft copolymers obtained by the cerium salt had narrow molecular weight distributions () compared with those by the APS catalyst in DMSO or water. The graft copolymers decomposed with sulfuric acid to isolate PMMAs, which molecular weights were larger than that of the corresponding homo-PMMAs. The structure of the grafted copolymers was characterized by IR, ¹³C NMR, DSC, and SEM. It was found that the graft copolymers exhibited the glass transition temperature (T_g), though curdlan had no T_g. As the grafting percentage increased, the T_g increased to reach 270°C, which was higher than the decomposition temperature of curdlan. The surface image of the grafted copolymers observed by SEM, showed smoothless compared with that of curdlan. It was also revealed that the graft copolymers having the grafting percentage of 1620% swelled in common organic solvents up to 4.5 times of the weight of the dry graft copolymer to form gels. © 1996 John Wiley & Sons, Inc.     

Graft copolymerization of 2-hydroxyethyl methacrylate and methyl methacrylate onto hide powder

Graft copolymerization of 2-hydroxyethyl methacrylate(HEMA) and mixtures of HEMA with methyl methacrylate (MMA) onto hide powder was attempted using ceric ammonium nitrate as initiator, with a view to optimize the conditions for graft copolymerization. Percent grafting and grafting efficiency were calculated for various variables such as monomer concentration, initator concentration and mole ratio of HEMA to MMA. R_p, R_g and R_h (rates of polymerization, grafting and homopolymerization respectively) were also evaluated. It was observed that R_p increased linearly with increasing concentration of MMA except at very low concentrations of the monomer. An explanation is given for the effect of variables on extent of grafting and grafting efficiency.     

Anionic graft copolymerization of methyl methacrylate with lithium diisopropylamide-treated poly(methyl α-substituted acrylate)s

The anionic grafting of methyl methacrylate onto several lithium diisopropylamide (LDA) — treated polymers of methyl α-substituted acrylates containing an active methylene or methine group was investigated. The grafting was carried out using a mole ratio of LDA/acrylate unit of 0.75 in the feed polymer. The anionic graft copolymerizability of these acrylate polymers largely depends upon the surrounding of the active α-hydrogen atom adjoining a carbonyl group or of the carbanion produced by the LDA treatment in the feed polymer.     

Graft copolymerization onto jute fiber: Ceric ion-initiated graft copolymerization of methyl methacrylate

Graft copolymerization of methyl methacrylate (MMA) was carried out on both defatted and bleached jute fibers using ceric ammonium sulfate (CAS) as the initiator. In order to obtain the optimum condition for grafting, the effects of initiator concentrations, temperature, time of reaction, lignin content of jute, and the monomer concentration were studied. The maximum percent grafting and grafting efficiency were found to be 132% and 0.71, respectively. Kinetic studies showed that at 0.03M CAS, the reaction appeared to obey the second-order process. The activation energies were found to be 7.74 and 5.12 kcal/mole for defatted (lignin content, 15.7%) and chlorite-bleached jute (lignin content 10%), respectively. The activation energies of graft copolymerization of MMA onto jute fiber are compared with the energies of activation of graft copolymerization of acrylonitrile (AN).     

Graft copolymerization onto rubber. V. Graft copolymerization of methyl methacrylate onto rubber using potassium peroxydiphosphate as initiator

The graft copolymerization of methyl methacrylate onto natural rubber (NR) is investigated using potassium peroxydiphosphate as the initiator. The rate of grafting is determined by varying monomer concentration, peroxydiphosphate concentration, and temperature. The graft yield increased with an increase in monomer concentration up to 1.4082M/L and thereafter the graft yield decreases. The graft yield increases significantly with an increase of peroxydiphosphate concentration up to 150 X 10^-1M/L and thereafter the graft yield decreases. The grafting reaction is temperature dependent. A suitable kinetic scheme is proposed and the rate equation is evaluated.     

Dimethyl 1-hexene-2,5-dicarboxylate,methyl methacrylate dimer,as polymerizable acrylic ester bearing bulky α-substituent

Dimethyl 1-hexene-2,5-dicarboxylate (MMAD), a methyl methacrylate dimer, which is an acrylic ester bearing a large α-substituent, was polymerized and copolymerized. During the bulk polymerization at room temperature, an ESR spectrum assigned to the propagating radical was observed. MMAD which polymerized much slower than methyl methacrylate (MMA) was less reactive in copolymerization than MMA. These findings may exemplify that slow propagation concomitant with termination suppressed with steric hindrance could lead to polymer formation of MMAD. Thermogravimetric analysis of poly(MMAD) exhibited that the degadation through depropagation was facilitated by the α-substituent. A relatively large chain transfer constant of MMAD in MMA polymerization, 9.8 × 10^?3, was evaluated consistent with a considerable decrease in the molecular weight of poly (MMA) in the presence of a small amount of MMAD.     

Emulsion copolymerization of styrene and methyl methacrylate

Chain transfer constants to monomer have been measured by an emulsion copolymerization technique at 44°C. The monomer transfer constant (ratio of transfer to propagation rate constants) is 1.9 × 10^?5 for styrene polymerization and 0.4 × 10^?5 for the methyl methacrylate reaction. Cross-transfer reactions are important in this system; the sum of the cross-transfer constants is 5.8 × 10^?5. Reactivity ratios measured in emulsion were r₁ (styrene) = 0.44, r₂ = 0.46. Those in bulk polymerizations were r₁ = 0.45, r₂ = 0.48. These sets of values are not significantly different. Monomer feed compcsition in the polymerizing particles is the same as in the monomer droplets in emulsion copolymerization, despite the higher water solubility of methyl methacrylate. The equilibrium monomer concentration in the particles in interval-2 emulsion polymerization was constant and independent of monomer feed composition for feeds containing 0.25–1.0 mole fraction styrene. Radical concentration is estimated to go through a minimum with increasing methyl methacrylate content in the feed. Rates of copolymerization can be calculated a priori when the concentrations of monomers in the polymer particles are known.     

Chemical initiation of graft copolymerization of methyl methacrylate onto styrene–butadiene block copolymer

When a solution containing both styrene–butadiene block copolymer (SBS) and methyl methacrylate is treated with an initiator both homopolymerization of the methyl methacrylate and graft copolymerization of the methyl methacrylate onto the SBS occur. The amount of graft copolymerization depends upon the time and temperature of the reaction, the concentrations of all species, and the identity of the solvent and initiator. The combination of benzoyl peroxide in chloroform gives the highest graft yield and the reaction occurs by removal of an allylic hydrogen from the SBS by the initiator radical and subsequent addition of monomer units to that site; there is a significant solvent effect. Both AIBN and BPO function by the removal of an allylic hydrogen atom from SBS; BPO is able to effect this reaction relatively easily while AIBN can remove the hydrogen atom only with great difficulty and to a limited extent. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 965–974, 1997     

Photosensitized copolymerization of optically active N-l-menthylmaleimide with styrene and methyl methacrylate

Photosensitized copolymerization of optically active N-l-menthylmaleimide (NMMI) with styrene (Sty) and methyl methacrylate (MMA) was carried out in tetrahydrofuran (THF) at 30°C with benzoyl peroxide (BPO). The monomer reactivity ratios for the copolymerization of NMMI (M₂) with Sty (M₁) and MMA (M₁) were r₁ = 0.08 ± 0.10, r₂ = 0.20 ± 0.05 and r₁ = 2.85 ± 0.06, r₂ = 0.07 ± 0.06, respectively. Copoly-MMA–NMMI and poly-NMMI showed positive circular dichroism(CD) curves of equal intensity and shape over the wavelength region from 230 to 270 nm; copoly-Sty–NMMI also showed a positive CD curve which was similar in shape but was different in intensity from that of poly-NMMI. The correlation between monomer unit ellipticity of the copolymers and their composition would suggest the alternating and stereoregular copolymerization of NMMI with Sty.     

Free-radical copolymerization of methyl methacrylate with styrene in the presence of 2-mercaptoethanol II. Influence of methyl methacrylate/styrene ratio

The free-radical copolymerization of methyl methacrylate (MMA) with styrene (St) in the presence of 2-mercaptoethanol (ME) was investigated in order to obtain ω-hydroxy oligomers with random copolymer-type chains of various compositions and molecular weights. Polymerizations at three different MMA/St molar ratios were carried out, while keeping constant the ME/monomer ratio. Monomer mixtures richer in MMA than in St were employed in order to attempt preparing lower polydispersity oligomers with monomodal molecular weight distribution (MWD). The molecular weights of the resulting oligomers increased with both conversion and MMA fraction in the feed, while polydispersities increased with conversion and decreased with MMA concentration in the initial monomer mixture. For the lower MMA fractions in the monomer feed, bimodal MWDs resulted beyond a certain conversion due to the faster relative consumption of ME than of monomer. Based on the pseudo-kinetic rate constant method, apparent chain transfer constants corresponding to the three different compositions of the monomer feed were estimated. The values obtained were in good agreement with the evolution of molecular weights and polydispersities with conversion and MMA fraction in the monomer feed. The co-oligomers prepared displayed functionalities around unity, making them suitable for the synthesis of macromonomers.     

Modeling of unseeded emulsion copolymerization of styrene and methyl methacrylate

A mathematical model for the unseeded emulsion copolymerization of styrene and methyl methacrylate has been developed. This model, which includes a new rate coefficient for radical desorption, was used to analyze the effect of the styrene/methyl methacrylate molar ratio in the initial charge on the number of particles, overall conversion and copolymer composition. It was found that the number of particles increased with the methyl methacrylate content and that a drift of the copolymer composition resulted during the polymerization of styrene/methyl methacrylate molar ratios other than 50/50. Good agreement between experimental results and model predictions was achieved.     

Free radical copolymerization of 1-vinyl naphthalene with styrene,methyl methacrylate,and acrylonitrile

Investigations on free radical copolymerization of 1-vinyl naphthalene (1-VNph, monomerM ₂) with styrene (St), methyl methacrylate (MMA) and acrylonitrile (AN) (monomersm ₁) in bulk at 60°C with AIBN as initiator are presented. Relative reactivity ratios were calculated by the Kelen-Tüdös method yielding:r _st=0.70 ±0.23 andr _1–VNph=2.02 ±0.40 for system St/1-VNph;r _MMA=0.32 ±0.10 andr _1–VNph=0.57 ±0.07 for system MMA/1-VNph andr _AN=0.11 ±0.03 andr _1–VNph=0.45 ±0.09 for system AN/1-VNph.Q, e values for 1-VNph according to Alfrey, Price scheme were calculated toQ _1–VNph=1.02,e ₁–VNph=–0.62.     

Grafting vinyl monomers onto wool fibers. III. Graft copolymerization of methyl methacrylate onto wool using hexavalent chromium ion

The use of hexavalent chromium to initiate graft copolymerization of methyl methacrylate onto wool fibers has been investigated. The rate of grafting was determined by varying monomer, chromium(VI), temperature, acidity of the medium, nature of wool, reaction medium, and redox system. The graft yield increases with increasing monomer concentration up to 0.65M, and, with further increase of monomer the graft yield decreases. The graft yield increases with increasing chromium(VI) concentration. The grafting is considerably influenced by chemical modification of wool prior to grafting. The effect of certain inorganic salt and anionic surfactant on the rate of grafting has been investigated. The graft yield is influenced by thiourea concentration; it decreases with increasing thiourea concentration.     

Grafting vinyl monomers onto silk fibers. IX. Graft copolymerization of methyl methacrylate onto silk using peroxydiphosphate-thiourea redox system

The graft copolymerization of methyl methacrylate (MMA) onto silk in aqueous media initiated by the potassium peroxydiphosphate-thiourea redox system was studied at 50°C. The rate of grafting was determined by changing [monomerl], [thiourea], [initiator], acidity of the medium, reaction medium, and temperature. A significant increase percent of grafting was noticed with increasing monomer concentration to 84.49 × 10^?2 mole/liter and the further increase is associated with the decrease of graft yield. The graft yield increases with an increase of thiourea (Tu) concentration to 25 × 10^?5 mole/liter; then it decreases. A measurable increase in graft yield was observed with an increase in acidity of the medium. Graft yield increases to a certain temperature, i.e., 50°C, and then it decreases. The graft yield increases with an increase of initiator concentration to 60 × 10^?4 mole/liter; then it decreases. The graft yield is medium dependent. A suitable kinetic path has been proposed and the rate equation has been derived.