Aqueous Tert-butyl Alcohol Research Articles

Gelatin-reinforced cellulose nanofiber composite cryogels for effective separation of small particulate matter in air

Herein, novel composite aerosol filters solely comprising renewable materials were designed using gelatin as a reinforcement agent and aqueous tert-butyl alcohol (TBA) as a dispersing medium for the cellulose nanofiber skeleton. The prepared composite cryogels exhibited distinct spider-web-like crosslinked structures and nanoporous architectures with porosity exceeding 98.8 % and density of less than 0.018 g/cm3. These composite filters exhibited high filtration efficiency and a robust and flexible mechanical structure due to gelatin reinforcement; furthermore, their quality factor exceeded the target threshold of 0.01 Pa−1 for 300 nm particle size. The filtration performance and mechanical properties of the composite filters could be tailored by adjusting the cellulose nanofiber (CNF), gelatin, and TBA contents, enabling the preparation of cryogels with a firm and strong structure. This study introduces ultraporous solids based on nanocellulose (NC) cryogels, which are promising, novel, and green materials for the production of advanced high-performance filter media for aerosol separation. Furthermore, the aforementioned approach is promising for the preparation of mechanically robust nanoporous biomaterials suitable for diverse applications such as heat and thermal insulation.

Quantifying the Nearly Random Microheterogeneity of Aqueous tert-Butyl Alcohol Solutions Using Vibrational Spectroscopy.

The microheterogeneous structure of aqueous tert-butyl alcohol (TBA) solutions is quantified by combining experimental, simulations, and theoretical results. Experimental Raman multivariate curve resolution (Raman-MCR) C-H frequency shift measurements are compared with predictions obtained using combined quantum mechanical and effective fragment potential (QM/EFP) calculations, as well as with molecular dynamics (MD), random mixture (RM), and finite lattice (FL) predictions. The results indicate that the microheterogeneous aggregation in aqueous TBA solutions is slightly less than that predicted by MD simulations performed using either CHARMM generalized force field (CGenFF) or optimized parameters for liquid simulations all atom (OPLS-AA) force fields but slightly more than that in a self-avoiding RM of TBA-like molecules. The results imply that the onset of microheterogeneity in aqueous solutions occurs when solute contact free energies are about an order of magnitude smaller than thermal fluctuations, thus suggesting a fundamental bound of relevance to biological self-assembly.

Influence of crowding on hydrophobic hydration-shell structure.

The influence of molecular crowding on water structure, and the associated crossover behavior, is quantified using Raman multivariate curve resolution (Raman-MCR) hydration-shell vibrational spectroscopy of aqueous tert-butyl alcohol, 2-butyl alcohol and 2-butoxyethanol solutions of variable concentration and temperature. Changes in the hydration-shell OH stretch band shape and mean frequency are used to identify the temperature at which the hydration-shell crosses over from a more ordered to less ordered structure, relative to pure water. The influence of crowding on the crossover is found to depend on solute size and shape in a way that is correlated with the corresponding infinitely dilute hydration-shell structure (and the corresponding first hydration-shell spectra are invariably very similar to pure water). Analysis of the results using a Muller-like two-state equilibrium between more ordered and less ordered hydration-shell structures implies that crossover temperature changes are dictated primarily by enthalpic stabilization of the more ordered hydration-shell structures.

Aggregation in dilute aqueous tert-butyl alcohol solutions: Insights from large-scale simulations

Molecular dynamics simulations employing up to 64,000 particles are used to investigate aggregation and microheterogeneity in aqueous tert-butyl alcohol (TBA) solutions for TBA mole fractions X(t) ≤ 0.1. Four different force fields are considered. It is shown that the results obtained can be strongly dependent on the particular force field employed, and can be significantly influenced by system size. Two of the force fields considered show TBA aggregation in the concentration range X(t) ≈ 0.03 - 0.06. For these models, systems of 64,000 particles are minimally sufficient to accommodate the TBA aggregates. The structures resulting from TBA aggregation do not have a well-defined size and shape, as one might find in micellar systems, but are better described as TBA-rich and water-rich regions. All pair correlation functions exhibit long-range oscillatory behavior with wavelengths that are much larger than molecular length scales. The oscillations are not strongly damped and the correlations can easily exceed the size of the simulation cell, even for the low TBA concentrations considered here. We note that these long-range correlations pose a serious problem if one wishes to obtain certain physical properties such as Kirkwood-Buff integrals from simulation results. In contrast, two other force fields that we consider show little sign of aggregation for X(t) ≲ 0.08. In our 64,000 particle simulations all four models considered show demixing-like behavior for X(t) ≳ 0.1, although such behavior is not evident in smaller systems of 2000 particles. The meaning of the demixing-like behavior is unclear. Since real TBA-water solutions do not demix, it might be an indication that all four models we consider poorly represent the real system. Alternatively, it might be an artifact of finite system size. Possibly, the apparent demixing indicates that for X(t) ≳ 0.1, the stable TBA aggregates are simply too large to fit into the simulation cell. Our results provide a view of the possible nature of microheterogeneity in dilute TBA-water solutions, and of the associated long correlation lengths. It is clear that system size can be a very important factor in simulations of these solutions, and must be taken into account in the evaluation and development of TBA-water force fields.

ChemInform Abstract: Novel Water-Soluble Diorganyl Tellurides with Thiol Peroxidase and Antioxidant Activity.

Novel water-soluble diaryl tellurides, alkyl aryl tellurides, and dialkyl tellurides carrying sulfopropyl groups were prepared and found to possess potent peroxide decomposing and chain-breaking antioxidative capacity. The dilithium, disodium, dipotassium, and bis-tetramethylammonium salts of bis(4-hydroxyphenyl) telluride (4) were treated with 2.3 equiv of 1,3-propanesultone in aqueous tert-butyl alcohol to give the corresponding salts 5 of bis-O-sulfopropylated diaryl telluride. A variety of diaryl ditellurides were reduced with sodium borohydride in ethanol. Upon addition of propanesultone to the resulting sodium arenetellurolates, the corresponding 3-aryltellurenylpropanesulfonic acid sodium salts 8 were precipitated. Diphenyl diselenide and dibutyl ditelluride reacted similarly to afford the sodium salts of 3-benzeneselenenylpropanesulfonic acid (9) and 4-telluraoctanesulfonic acid (10), respectively. The glutathione peroxidase-like activity of the water-soluble compounds was assessed at pH = 7.4 by ...

Routes to Alkene and Epoxide Functionalized Nanoporous Materials from Poly(styrene-b-isoprene-b-lactide) Triblock Copolymers

Nanoporous materials with inherently tunable surface chemistries are poised to have a considerable impact in catalysis, separations, and nanopatterning. Using core−shell cylinder forming polystyrene-b-polyisoprene-b-polylactide (PS−PI−PLA) triblock terpolymers as templates, we were able to prepare aligned PI-coated nanoporous PS monoliths via the degradative removal of the cylindrical PLA cores. PS−PI−PLA precursors were synthesized using a combination of anionic (PS, PI) and ring-opening (PLA) polymerizations. The degree of order, alignment, and PLA degradation achievable was a strong function of molecular weight at a given triblock terpolymer composition. For intermediate molecular weight samples (25−28 kg mol-1), greater than 95% of the PLA was hydrolyzed through exposure of the monolith to a 0.1 wt % sodium dodecyl sulfate (SDS) solution in 0.5 N NaOH. However, low (17.5 kg mol-1) and high (46.8 kg mol-1) molecular weight samples of identical composition showed considerable resistance to PLA degradation. Treatment of the degraded monoliths with m-chloroperoxybenzoic acid in aqueous tert-butyl alcohol solutions permitted the controlled epoxidation of up to 75−80% of the PI alkene units. Despite some loss in pore alignment, scanning electron microscopy and small-angle X-ray scattering verified the retainment of the nanoporous structure following epoxidation.

Determination of Temperatures within Acoustically Generated Bubbles in Aqueous Solutions at Different Ultrasound Frequencies

Mean acoustic bubble temperatures have been measured using a methyl radical recombination (MRR) method, at three ultrasound frequencies (20, 355, and 1056 kHz) in aqueous tert-butyl alcohol solutions (0-0.5 M). The method is based on yield measurements of some of the hydrocarbon products formed from the recombination of methyl radicals that are thermally generated within collapsing bubbles containing tert-butyl alcohol vapor. The mean bubble temperatures were found to decrease substantially with increasing tert-butyl alcohol concentration at 355 and 1056 kHz but only to a small extent at 20 kHz. Extrapolating the mean temperatures measured to zero concentration of tert-butyl alcohol, at a bulk solution temperature of 20 degrees C, gave the order 355 kHz (4300 +/- 200 K) > 1056 kHz (3700 +/- 200 K) > 20 kHz (3400 +/- 200 K). It is also concluded that the temperature derived from the MRR method is a useful diagnostic parameter for sensing the thermal conditions within an active acoustic bubble. However, attention must be given to the fact that the temperature derived from the MRR method is not theoretically well defined.

Alkenecis-Dihydroxylation by [(Me3tacn)(CF3CO2)RuVIO2]ClO4(Me3tacn = 1,4,7-Trimethyl-1,4,7-triazacyclononane): Structural Characterization of [3 + 2] Cycloadducts and Kinetic Studies

cis-Dioxoruthenium(VI) complex [(Me(3)tacn)(CF(3)CO(2))Ru(VI)O(2)]ClO(4) (1, Me(3)tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) reacted with alkenes in aqueous tert-butyl alcohol to afford cis-1,2-diols in excellent yields under ambient conditions. When the reactions of 1 with alkenes were conducted in acetonitrile, oxidative C=C cleavage reaction prevailed giving carbonyl products in >90% yields without any cis-diol formation. The alkene cis-dihydroxylation and C=C cleavage reactions proceed via the formation of a [3 + 2] cycloadduct between 1 and alkenes, analogous to the related reactions with alkynes [Che et al. J. Am. Chem. Soc. 2000, 122, 11380]. With cyclooctene and trans-beta-methylstyrene as substrates, the Ru(III) cycloadducts (4a) and (4b) [formula; see text] were isolated and structurally characterized by X-ray crystal analyses. The kinetics of the reactions of 1 with a series of p-substituted styrenes has been studied in acetonitrile by stopped-flow spectrophotometry. The second-order rate constants varied by 14-fold despite an overall span of 1.3 V for the one-electron oxidation potentials of alkenes. Secondary kinetic isotope effect (KIE) was observed for the oxidation of beta-d(2)-styrene (k(H)/k(D) = 0.83 +/- 0.04) and alpha-deuteriostyrene (k(H)/k(D) = 0.96 +/- 0.03), which, together with the stereoselectivity of cis-alkene oxidation by 1, is in favor of a concerted mechanism.

Pressure-Enhanced C−H···O Interactions in Aqueous tert-Butyl Alcohol

We have investigated pressure-enhanced C−H···O interactions in tert-butyl alcohol (TBA)/D2O mixtures. On the basis of its responses to changes in pressure and concentration, TBA appears to be the ideal candidate to study the variations in structural and dynamical properties of C−H···O interactions. For dilute aqueous TBA, the pressure dependence of the C−H bands yielded blue frequency shifts at pressures below 0.3 GPa, but an increase in pressure leads to a red frequency shift at pressures above this value. This discontinuity in frequency shift is related to enhanced C−H···O interactions. The frequency of the C−H stretching modes that characterize C−H···O hydrogen bonding undergoes a blue shift with pressure. This behavior is in contrast with the general trend of red shifts observed in strongly hydrogen-bonded systems that occur through O−H···O and CO···H interactions. We discuss the results of density functional theory calculations that predict the frequency shift of the C−H stretching vibrations.

Vibrational spectroscopic studies of aqueous solutions of tert-butyl alcohol and tert-butylamine

Raman and FT-IR absorption spectra of aqueous tert-butyl alcohol (t-BuOH) and tert-butylamine (t-BuNH2) in the region of the O–H and NH2 stretching and bending modes have been measured as a function of organic co-solvent concentration in the whole co-solvent mole fraction region. The major observed changes of the aqueous binary solution spectra compared with the solvent spectra are a loss or gain of band intensity. In particular, the observed changes in intensities and linewidths of some bands were significantly more pronounced at low concentrations of organic co-solvents in water, where t-BuOH and t-BuNH2 tend to integrate into the water structure. Clear evidence of structural enhancement of the network is obtained in dilute solutions as well as destruction of the network by hydrophobic interactions as the concentration is increased. Generally, the interpretation of the spectra is in agreement with the capacity of the hydrophobic co-solvent to break the structure of water in the more concentrated aqueous solutions and to enhance the structure in dilute solutions. Vibrational intensities and frequency shifts of some bands show definite trends with varying the concentration of the solutions. In the concentration-dependence study, unusual linewidth changes of certain bands were observed.Key words: infrared, Raman spectra, aqueous, tert-butanol, tert-butylamine.

Interfacial Properties of tert-Butyl Alcohol Solutions and Their Relation to Clathrate Formation

According to a previous report (Glinski, J.; et al. J. Chem. Phys. 1996, 102, 8816) the surface entropy of the tert-butyl alcohol/water system shows a maximum with respect to solute concentration. Such a maximum was formerly related to the formation of clathrate structures at the interfacial region. However, more complex behavior has also been observed in other aqueous systems. It is currently believed that the surface entropy maxima may reflect structural changes similar to a phase transition and specific interactions between solute molecules. To test the clathrate hypothesis, the thermodynamic properties of tert-butyl alcohol at water, heptane, and water/heptane interfaces were evaluated. For this purpose, the variation of the surface/interfacial tension as a function of temperature and solute concentration was measured, employing Wilhelmy plate and Du Nouy ring techniques. In aqueous tert-butyl alcohol solutions, the maximum of entropy found by Glinski et al. is reproduced. The absence of a large maxim...

Influence of Alkyl Substitution on the Gas-Phase Stability of 1-Adamantyl Cation and on the Solvent Effects in the Solvolysis of 1-Bromoadamantane

1-Adamantyl cations having three methyl groups or one, two, or three isopropyl groups on the 3-, 5-, and 7-positions were found by FT ICR to be more stable than the 1-adamantyl cation and that the stability increases with the number of isopropyl group. The relative stabilities calculated by PM3 were in good agreement with the experimental results. In contrast, the sequence of the rates for the solvolysis in nonaqueous solvents are 3,5,7-(Me)(3)-1-AdBr < 1-bromoadamantane (1-AdBr) < 3,5,7-(n-Pr)(3)-1-AdBr < 3,5,7-(i-Pr)(3)-1-AdBr. The rates of solvolysis of 3,5,7-(i-Pr)(3)-1-AdBr and 3,5,7-(n-Pr)(3)-1-AdBr relative to 1-AdBr at 25 degrees C are 15 and 3.8 in EtOH, respectively, but markedly decreases with the increase in the amount of added water, reaching 0.84 and 0.15, respectively, in 60% EtOH. Reflecting these effects of water, the Grunwald-Winstein (GW) relationship for 3,5,7-(i-Pr)(3)-1-AdBr and 3,5,7-(n-Pr)(3)-1-AdBr against Y(Br) is linear for nonaqueous alcohols (EtOH, MeOH, TFE-EtOH, TFE, 97% HFIP), but marked downward deviations are observed for aqueous organic solvents, in particular, aqueous ethanol and aqueous acetone. The effect of the alkyl substituents to diminish relative solvolytic reactivity in EtOH-H(2)O mixtures may be ascribed to a blend of steric hindrance to Betarphinsted base-type hydration to the beta-hydrogens and hydrophobic interaction of the alkyl groups with ethanol to make the primary solvation shell less ionizing. The introduction of one nonyl group to the 3-position showed much smaller deviations in the GW relationship than the case of 3,5,7-(n-Pr)(3)-1-AdBr. The markedly decelerated solvolysis of alkylated 1-bromoadamantanes in aqueous organic solvents is a kinetic version of anomalously diminished dissociation of alkylbenzoic acids in aqueous ethanol and aqueous tert-butyl alcohol that was demonstrated by Wepster and co-workers a decade ago and ascribed to hydrophobic effects.

Engineering chloroperoxidase for activity and stability

Random mutagenesis of Caldariomyces fumago was carried out to produce a chloroperoxidase (CPO) with enhanced activity in mixtures of aqueous buffers and organic cosolvents. A mutant CPO with a 3.4-fold increased activity in 40% aqueous tert-butyl alcohol was obtained.A CPO-surfactant conjugate, prepared by colyophilisation, mediated the oxidation of thioanisole to its (R)-sulfoxide by TBHP in water-saturated isooctane. Copolymerisation of CPO and a toluenediisocyanate prepolymer resulted in a stable preparation that mediated the oxidation of indole to 2-oxindole in a range of organic solvents. The highest yield was obtained in 1-octanol.

Hydrophobic hydration of tert-butyl alcohol probed by NMR and IR

The hydrophobic hydration in aqueous tert-butyl alcohol(TBA) mixtures was studied by examining the concentration and the temperature dependences of 1H and 13C chemical shifts in NMR, together with the concentration dependence of the frequency for the CH stretching vibration band, νCH. The chemical shifts were measured with the external double reference method, with which the bulk volume magnetic susceptibility for every sample mixture was also obtained to be used for the correction of the chemical shifts in situ. The polarization of the water molecules in the mixture probed by the 1H chemical shift, ∗δH2O, varies with concentration; δH2O increases at 23.3°C from 3.5 ppm in the TBA-rich region to the value for pure water at the mole fraction of water χW=0.84 and reaches to the maximum at χW=0.95. In the region of 0.84<χW<1.0, δH2O is larger than that for pure water, indicating clearly the presence of highly polarized or strongly hydrogen-bonding water molecules compared with pure water. The νCH also continues to increase with increasing χW from 2973.6cm−1 for pure TBA gently up to χW=0.84 and then steeply up to χW=0.95 to reach 2980.3cm−1, then remains constant up to the measurable concentration limit, χW=0.99. The polarization of TBA molecule was also found to increase in the same way as νCH. These results not only indicate the formation of associated complexes of TBA with water molecules, but also confirm the formation of polyhedron or cluster so far presented for mixing state in water-rich region. In addition to this the results show that the hydration of CH groups occurs through a kind of dispersion interaction between CH group and water oxygen, in which contraction of the CH bond occurs as demonstrated by the blueshifts of the CH stretching vibration band. The new mechanism of CH hydration, termed “push ball” hydration, is proposed.

Transfer Thermodynamic Functions ∆Gt0, ∆Ht0 and T∆St0 of cis- and trans-[CoCl2(en)2]+ Isomers in Aqueous Mixtures of Methanol, tert-Butyl Alcohol and Acetonitrile

The solubility, partial molar volume and standard integral molar enthalpy of solution of cis- and trans-[CoCl2(en)2]Cl in water, aqueous methanol, aqueous tert-butyl alcohol and aqueous acetonitrile are reported. The transfer functions ∆Gt0, ∆Ht0 and T∆St0 as well as partial molar volumes are used to obtain information on the solute-solvent interactions. Results obtained are discussed in terms of differences in the surface charge distribution in isomeric coordination species.

The degradation of glycoproteins with lithium borohydride: Isolation and analysis ofO-glycopeptides with reducedC-terminal amino acid residue

By the example of fetuin and a blood-group-specific mucin from porcine stomach, we showed that, under conditions of reductive degradation of glycoproteins with LiBH4-LiOH in 70% aqueous tert-butyl alcohol, the reduction and cleavage of amide bonds occur much faster than the simultaneous beta-elimination of carbohydrate chains O-linked with Ser and Thr residues of the peptide chain. The major degradation products containing the O-linked glycans are the O-glycosylated derivatives of 2-aminopropane-1,3-diol and 2-aminobutane-1,3-diol (the products of reduction of glycosylated Ser and Thr) and the glycopeptides containing 2-4 amino acid residues with reduced C-terminal amino acid. Seventeen homogeneous O-glycopeptides were isolated from the fetuin degradation products by ion-exchange and reversed-phase HPLC. Their structures were determined by MALDI-TOF mass spectrometry and by analyses for amino acids, amino alcohols, and carbohydrates. The application of the reaction for characterization of O-glycans and localization of O-glycosylation sites in O- and N,O-glycoproteins is discussed.

Novel Water-Soluble Diorganyl Tellurides with Thiol Peroxidase and Antioxidant Activity.

Novel water-soluble diaryl tellurides, alkyl aryl tellurides, and dialkyl tellurides carrying sulfopropyl groups were prepared and found to possess potent peroxide decomposing and chain-breaking antioxidative capacity. The dilithium, disodium, dipotassium, and bis-tetramethylammonium salts of bis(4-hydroxyphenyl) telluride (4) were treated with 2.3 equiv of 1,3-propanesultone in aqueous tert-butyl alcohol to give the corresponding salts 5 of bis-O-sulfopropylated diaryl telluride. A variety of diaryl ditellurides were reduced with sodium borohydride in ethanol. Upon addition of propanesultone to the resulting sodium arenetellurolates, the corresponding 3-aryltellurenylpropanesulfonic acid sodium salts 8 were precipitated. Diphenyl diselenide and dibutyl ditelluride reacted similarly to afford the sodium salts of 3-benzeneselenenylpropanesulfonic acid (9) and 4-telluraoctanesulfonic acid (10), respectively. The glutathione peroxidase-like activity of the water-soluble compounds was assessed at pH = 7.4 by using the coupled GSSG reductase assay. Dialkyl telluride 10 turned out to be the most efficient catalyst. Several alkyl aryl tellurides 8 were also more efficient than any of the previously tested organotellurium compounds in this model. Bulky and electron-withdrawing aryl substituents seemed to reduce activity, whereas electron-donating groups enhanced it. Alkyl aryl selenide 9 was void of any catalytic activity. The novel compounds were also assessed by (1)H NMR spectroscopy for their capacity to catalyze the hydrogen peroxide oxidation of N-acetylcysteine in D(2)O under acidic conditions. In the presence of 0.01 mol % of the organotellurium catalyst, the thiol concentration was reduced to 50% within 12 min for the most active catalyst (compound 5b). Although many of the compounds showed high catalytic activity, it was not possible to rationalize their relative efficiency. The capacity of the novel organotellurium compounds to act as a scavengers of 1,1-diphenyl-2-picrylhydrazyl (DPPH) was also investigated. The organotelluriums seem to act primarily as electron donors in their reaction with DPPH. Compounds 8d, 10, and 8b were the most effective scavengers. Bulky or electron-withdrawing aryl substituents caused a reduction in activity, whereas electron-donating ones enhanced it. None of the compounds could match vitamin E in their scavanging capacity.

Diffusion and Structure in Dilute Aqueous Alcohol Solutions: Evidence for the Effects of Large Apolar Solutes on Water

By measuring the dependence of molecular motion on pressure, p, using diffusion measurements as a probe, one can obtain information regarding the structure of solutions containing amphiphilic solutes having apolar or hydrophobic groups. We have found that at low temperatures, the intra-diffusion coefficient (D) of water in a dilute solution of aqueous tert-butyl alcohol (mole fraction, x = 0.025) shows a maximum with increasing p, to a greater relative extent than in pure water under the same conditions. This suggests the water in these solutions is more “structured” than in pure water, though there is a clear distinction from the effects produced by large “structure breaking” ions as solutes where the absolute water diffusion coefficient may show a maximum as concentration or pressure is increased. We have made a survey of a number of other water−alcohol systems; a similar large enhancement occurs in 2-propanol solutions. In solutions of methanol, ethanol, and 2,2,2-trifluoroethanol, the enhancement is similar to that of water with no additional effect. Volumes of activation (ΔVD) have been calculated from the diffusion data. From an analysis of the T and p dependence of D and ΔVD, we have concluded that the mechanism for the diffusion of water in these solutions seems likely to be the same as for pure water. The molecules can move around the obstacle solute molecules via the labile hydrogen-bonded network. Where the temperature is low and the solute alcohol molecules are large, the network appears to be distorted such that the effect of pressure on water diffusion is greater with the maximum appearing at higher pressures than in pure water.

Solubility and Thermodynamic Transfer Functions of Cesium Dianilinetetraisothiocyanatochromate(III)

The solubilities of cesium dianilinetetraisothiocyanatochromate(III) in water as well as in aqueous methanol, isopropyl alcohol, tert-butyl alcohol and acetonitrile were measured as a function of temperature and solvent composition. The Gibbs energies, enthalpies and entropies of transfer of the salt from water to the given solvents have been evaluated from experimental data. The contribution of [Cr(C6H5NH2)2(NCS)4]- ion to the Gibbs energy of transfer of the investigated salt has been calculated using the tetraphenylarsonium tetraphenylborate (TATB) reference electrolyte assumption.

Dispersion Polymerization of Acrylamide

Dispersion polymerization of acrylamide has been successfully carried out in aqueous tert-butyl alcohol (TBA) media (TBA = 50 - 80 vol %) using poly(vinyl methyl ether) (PVME) as the polymeric stabilizer and ammonium persulfate as the initiator. Polydisperse spherical as well as oval particles are formed. The simultaneous presence of both spherical and oval particles suggests the coalescence of similar size particles (homocoalescence) takes place, leading to polydispersity. The increase of stabilizer concentration leads to a decrease in particle size and an increase in molecular weight. An increase of initiator concentration results in an increase in particle size and a decrease in molecular weight. These observations are in conformity with other dispersion polymerizations reported in the literature. Particle size decreases as the TBA concentration increases, i.e. as the medium polarity decreases. TBA-water mixtures exhibit cosolvency toward PVME, the solvency becoming highest at about 70 vol % TBA. This solvency aspect cannot account for the monotonous decrease of particle size with an increase in TBA concentration. A plot of particle diameter (D n ) vs the initial solubility parameter (δ) of the medium gives a straight line unlike the linear relationship between D n and 1/δ reported for dispersion polymerization of nonpolar monomers in polar solvents. This difference in behavior for the two systems can be reconciled ifthe grafted polymer acts as the true stabilizer.