Associative properties of hydrophilic tip modified oxyethylene‐oxybutylene diblock copolymers in aqueous media: Effect of end‐group

Abstract

The associative properties of Me 2 N (CH 2 ) 2 OE 58 B 7 and I À Me 3 N þ (CH 2 ) 2 OE 58 B 7 in aqueous solution in the temperature range of 20-50 C have been investigated by dynamic and static laser light scattering. Here E represents an oxyethylene unit and B an oxybutylene unit. The results obtained were compared with results for E m B n analog. Our result shows that for micelles of dimethylamino-tipped, the hydrodynamic radius, was large as compared with the thermodynamic radius r t , suggesting a ''soft'' micelle. For the trimethylammonium-tipped copolymer, r h decreases and r t increase with the increase in temperature. Also the values of association number, N w , were low but increase with increase in temperature, indicating a change from soft micelle at low temperature to small, less swollen micelles at high temperature. The high values of thermodynamic volume per molecule, r t /N w , for a polymer with charged tip could be attributed to intermicellar charge effect. The effect of salt on various micellar parameters has also been discussed. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: [951][952][953][954][955][956][957] 2012

Preparation, physicochemical and stability studies of chitosan-PNIPAM based responsive microgels under various pH and temperature conditions

“…The normalization of I(log D h,app ) gave intensity fraction distributions. Average values of Γ, delivered by the CONTIN program by integration over the intensity distributions, were similarly converted to intensity-average values of D h,app [37,38]. It is important to mention here, that the values of sizes (D h ) given in this paper are the average values; and hence, slightly overestimated, as soft particles possess lower D h than the real hard sphere ones for frictional reasons.…”

“…(1), the scattering vector q = (4π n/ ) sin(θ/2), n is the refractive index of the solvent, and θ is the scattering angle. Supposing that the particles are solid, the apparent diffusion coefficient was then converted to an apparent hydrodynamic diameter [D h,app , diameter of the hydrodynamically equivalent hard sphere, corresponding to the apparent diffusion coefficient (D app )], using the StokesEinstein relationship [38]:…”

Synthesis, physicochemical studies and potential applications of high-molecular-weight ferrocene-based poly(azomethine)ester and its soluble terpolymers

“…Hence, distributions of apparent hydrodynamic radius (R h,app ) were evaluated using the StokeseEinstein relationship R h,app ¼kT/(6phD app ), where k is the Boltzmann constant, T is the absolute temperature and h is the viscosity of the solvent. The hydrodynamic radius R h reflects the physical dimensions of the polymer chains, as it involves both the chain and the amount of the solvent associated with, whereas the radius of gyration R g is related to the size of chain and in other words to the excluded volume of polymer in the solvent and mostly depends on the thermodynamic quality of the solvent [30,32]. Moreover the ratio R g /R h reflects the chain conformation.…”

Associative, thermodynamic and thermo-kinetics behavior of di- and triblock copolymers of oxyethylene and oxybutylene in aqueous media

“…The torsion balance was calibrated and checked for zero with water before any new measurements. Following the previous practice [20][21][22]34], the CMC was determined from the plots of surface tension (g) versus log C as the concentration at which a constant value of g was established.…”

“…The length and nature of hydrophobic block mainly affect CMC, aggregation number and thermodynamic parameters like enthalpy, entropy and free energy of micellization while the hydrophilic block mainly control the micellar size and interaction parameters [20]. Similarly, changing the solution temperature can also greatly alter various surface and thermodynamic properties of these amphiphilic self-assembly systems [21,22]. Likewise, a number of micellar parameters can also be adjusted by varying the solution composition by using co-solvent and co-solutes [23,24].…”