Pedro M. Sasia

Interpenetration functions and excluded-volume theories in relation to light scattering data from poly(phenyl acrylate) solutions

Light scattering measurements have been made on dilute solutions of poly(phenyl acrylate) in ethyl lactate at 10 temperatures ranging from the θ temperature (284.7 K) up to 379 K to yield the weight-average molar mass Mw (= 1.46 × 106g mol−1), the second virial coefficients A2 and the mean-square radii of gyration 〈S2〉. Chain expansion factors αs obtained via 〈S2〉 were used to calculate the excluded-volume functions according to different theories, and the interpenetration function ψ was calculated from Mw, A2 and 〈S2〉. The results are discussed in relation to consistent pairs of theoretical expressions for the excluded-volume function and ψ.

Preferential and total sorption in the system PMMA/toluene + n-butyl chloride

Abstract The solution properties of poly(methyl methacrylate) in binary mixtures of toluene with n-butyl chloride have been studied by densitometry, dialysis equilibrium differential refractometry and viscometry. Attempts have been made to fit the experimental results using various theoretical expressions for the preferential and total sorption coefficients, based on various assumptions. An explanation of the agreement or disagreement between experimental and theoretical results is proposed on the basis of specific solute-solvent interactions.

Synthesis and Characterization of Polyacrylamides in Inverse-Emulsions with an Isoparaffinic Solvent

Inverse-emulsion polymerizations of aqueous solutions of acrylamide (AM) in an isoparaffinic solvent were carried out using Span 80 as emulsifier. The conversions at the end of inverse-emulsion polymerizations were investigated by HPLC methods. The conversion has been influenced by the initiator concentration, the monomer concentration and the reaction temperature. The molar masses were determined by viscosity measurements, size exclusion chromatography (SEC) and static light scattering. The influence of initiator concentration, monomer concentration and reaction temperature on the average molar mass of polyacrylamide (PAM) was studied

Anomalous behaviour of PMMA in the (methyl isobutyl ketone)/methanol system

Abstract We have studied the solution properties of PMMA in mixtures of methyl isobutyl ketone with methanol by viscometry and laser light scattering. The results indicate that this system shows a conformational transition in the polymer chain in the composition interval of 10–14% (v/v) of methanol. An explanation of this transition is proposed on the basis of specific solute-solvent interactions.

Variation in thermodynamic properties of polymethacrylates in binary mixtures

Abstract Viscometric, densitometric and light scattering measurements have been performed for poly(methyl methacrylate), poly( n -butyl methacrylate) and poly(cyclohexyl methacrylate) binary mixtures of toluene and n -butyl chloride at 298 K. The total sorption to the polymer chain by the solvents, the Mark-Houwink-Sakurada parameter and the interaction parameter, B , have been determined. Conclusions about the liquid-liquid and polymer-liquid interactions have been drawn, trying to explain the influence of the polymer side group on solution behaviour.

Thermodynamic magnitudes of l-menthol/-acetonitrile and l-menthol/carbon tetrachloride binary mixture by VPO

Abstract In this paper we have studied the thermodynamic behaviour of l -menthol in acetonitrile and carbon tetrachloride by vapour pressure osmometry (VPO) in the temperature range 303–323 K. We have found that l -menthol behaves in a different way in both solvents. From osmotic coefficients we have calculated the excess functions of the system. In l -menthol/carbon tetrachloride we have found a great deviation from ideal behaviour, on the contrary, the deviation is very slight in the other system. This circumstance hinders the study of this system with VPO. The behaviour of l -menthol in carbon tetrachloride has been discussed as a function of molecular interactions. Finally, self-association phenomena have been detected. By means of theoretical models the association number has been calculated.

Preferential adsorption behaviour of several vinyl polymers in poly(ethylene glycol)(1)/THF(2)

SummaryThe preferential sorption coefficient in the ternary systems vinyl polymers (3)/Poly (ethylene glycol) (1)/THF(2) has been determined in dilute solutions by dialysis equilibrium differential refractometry at 633 nm and 298 K. A series of vinyl polymers of different side groups (Polystyrene, Poly (p-iodostyrene), Poly (n-vinyl carbazole), Poly (vinyl chloride) and Poly (methyl methacrylate)) has been studied.The results indicate that polymer side group play a fundamental role in the solvation behaviours of vinyl polymers. The characteristics of the polymer side group influences the kind and intensity of the polymer-binary solvent interactions and so, the rest of solution properties of these systems.

Stability of inverse microemulsions of acrylamide-based anionic flocculants: evidence about the need of unsaturated surfactants

Abstract Influence of surfactant structural characteristics on stability of inverse microemulsions of acrylamide-based anionic flocculants (40% (w/w) sodium acrylate and 60% (w/w) acrylamide, based on total amount of comonomers) has been studied by using 17 surfactant blends consisting of two non ionic surfactants with different length of hydrophobic chains, different number of hydrophobic chains per molecule, and with and without double bonds on their hydrophobic chains. Experimental evidence shows that unsaturated emulsifiers are needed for obtaining stable inverse microemulsions of acrylamide-based anionic flocculants and that presence of double bonds on the hydrophobic tails of a surfactant is its major structural characteristic to stabilize this kind of polymeric inverse microemulsions (PIM).

Synthesis of cationic flocculants based on acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride copolymers by semicontinuous inverse microemulsion polymerization. Part III: influence of HLB and surfactant blend concentration on flocculating performance

Abstract The influence of HLB (hydrophilic-lipophilic balance) and surfactant blend concentration (SBC) on flocculating performance of latex particles of acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride copolymers with a cationic charge density of 40%, obtained by inverse microemulsion copolymerization by using a surfactant blend of Arlacel 83 and Softanol 90 as emulsifier and Rolling M-245, a mixture of n-decane and n-tetradecane in about 40/60 weight ratio, as oil phase, has been studied for a total comonomer concentration of 32.5% (w/w). Comonomer inverse microemulsion copolymerizations were carried out in the semicontinuous mode by adding continuously an aqueous solution of sodium metabisulfite (SMB) as initiator into stirred inverse comonomer microemulsions. From 7.75 to 8.26, HLB has a strong influence on average molar mass (Mw) and flocculating performance (FP), the higher the HLB the higher the FP. A small decrease in SBC causes a dramatic increase in Mw and a decrease in FP although the influence on copolymer viscosity is small. Results are explained in terms of copolymer structuring degree and collapsed state of copolymer chains inside latex particles as well as in terms of the observed composition drift with conversion.

Synthesis of cationic flocculants based on acrylamide and (2-(acryloyloxy)ethyl)trimethylammonium chloride co polymers by semicontinuous inverse microemulsion co polymerization. Part I: Criteria for selection of comonomer formulation

Abstract The influence of surfactant blend composition, organic solvent (oil) structure and cationic charge density (CCD) on stability of comonomer inverse microemulsions of acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride has been studied in order to obtain criteria for selecting comonomer inverse microemulsions before copolymerization resulting in copolymer inverse microemulsion useful as flocculants. Results show that optimum HLB can be explained by cohesive energy ratio theory and it increases with CCD; the higher the hydrophobic chain length of surfactants in surfactant blend, the lower the minimum surfactant blend concentrations (SBCm) needed to obtain stable inverse microemulsions; and linear organic solvents allow a decrease of the SBCm required for stabilizing comonomer inverse microemulsions.