Interpolymer association

R. M. Kowalik, I. Duvdevani, R. D. Lundberg, D. N. Schulz, D. G. Peiffer, and K. Kitano. Enhanced drag reduction via interpolymer associations. J Non-Newtonian Fluid Mech, 24(1) 1-10, April 1987. 

Kowalik RM, Duvdevani I, Peiffer DG, Lundberg RD, Kitano K, Schulz DN (1987) Enhanced drag reduction via interpolymer associations J Non-Newton Fluid Mech 24 1... 

Eustace, D. J. Siano, D. B. Drake, E. N., "Polymer Compatibility and Interpolymer Association in the Poly(Acrylic Acid)-Polyacrylamide- Water Ternary System," J. Appl. Polym. Sci., 35, 707 (1988). 

Li et al. [44] found that the addition of the zinc salt of sulfonated atactic polystyrene to sPS in amounts lower than 10wt% decreases both the crystallization rate and the crystallite size and perfection of sPS. On the other hand, above this content, only minor influences on the properties of sPS are observed. The authors concluded that in the latter case interpolymer association of the ionic groups causes greater liquid-liquid separation, so supporting the hypothesis of substantial incompatibility between such polymers. 

MYL Mylonas, Y., Bokias, G., lliopoulos, L, and Staikos, G., Interpolymer association between hydrophobically modified poly(sodium aciylate) and poly(Y-isopropyl-aciylamide) in water The role of hydrophobic interactions and polymer structure,... 

Fig. 41 (a) Model of a ladder-like polymer formed by interpolymer associations (highlighted by red dashed lines) [279]. The flow direction is horizontal, (b) Increase of the maximnm Icmgth permissible Wiad/Min in the ease of a ladder-like polymer as compared to a linear polymer, for the same fracture force. The legend indicates different normalized bead size ajh. (Adopted with permission from Agarwal et al. [279]. Copyright 1994 American Institute of Physics)... 

Physical gelation by another interaction was investigated, using side groups with a strong tendency for interpolymer association such as long alkyl chains or... 

INTERPOLYMER ASSOCIATION OF EXCIPLEX FORMING POLYMERS UNDER EXTREMELY DILUTE CONDITIONS... 

The driving factors for interpolymer association are in principle same as those for small molecular systems. 

Any intermolecular interactions observable in small molecular systems such as hydrogen bonding, EDA interaction, Coulombic force, and hydrophobic interaction are operative in any interpolymer association phenomena. When any interacting groups are incorporated in polymers, the molecular interactions of the polymer with either small molecules or polymers are in general enhanced unless steric hindrance comes in effect. 

Interpolymer association has been most widely studied for polyelectolytes and hydrogen bonding polymers. Besides complex formation between polycation and polyanion represented by the complexes between polyionenes and poly(methacrylic acid) (7), the association of poly(carboxylic acid) with proton accepting polymers such as poly(ethylene oxide), poly(N-vinyl-2-pyrrolidone), and poly(vinyl alcohol) is the subject of active research (8). The main binding forces are attributed to Coulombic and hydrogen bonding interactions. The role of hydrophobic interaction cannot, however, be neglected. The different behaviors of poly(meth-acrylic acid) and poly(acrylic acid) in complex formation evidence the importance of hydrophobic interaction (9). 

Hydrophobic association is also enhanced in polymer systems. Although polymer surfactants are considered to form micelles via intrapolymer hydrophobic interaction, our recent study (2r,s) revealed that a polyionene bearing anthryl groups as the hydrophobic domain showed a clear cmc UHtical micelle concentration) at the segment concentration around 3 x 10 5m. Reference experiments with a polyionene without anthryl groups and the monomer and dimer model compounds have indicated that the cmc is particularly low for the polymer. Taking the excimer intensity of anthracene fluorescence as an index of interchromophore interaction, we confirmed the existence of interpolymer association by the concentration dependent excimer intensity. Under the same condition to the polymer, any model systems either monomeric or dimeric do not associate intermolecularly. 

The interpolymer association is a distinctively different property of exciplex forming polymers from that of excimer forming polymers. The reason must be attributed to the presence of the ground state interaction in the former polymers. Interpolymer excimer formation is, however, facilitated by the aid of hydrophobic interaction in water. Polyionenes bearing anthryl groups (J2) form both inter- and intrapolymer excimer in water (2s). The excimer intensity decreases with increasing hydrophobic interaction. All experimental results indicate that weak intermolecular interactions almost undetectable in small molecule systems are amplified enormously in polymer systems in dilute solutions. 

In the following sections, we will discuss the solvent and molecular weight effects on the interpolymer association of pyrene - N,N-dimethylaniline exciplex forming polymers. 

Several years ago we observed that the interpolymer association came in effect when DP of exciplex forming polymers exceed a certain threshold value (2v). For the exciplex formed between carbazolyl and terephthalate incorporated in a polyester, the exciplex emission was concentration independent for the dimer model or oligomers. The polyester(DP> 10), however, behaves differently and the exciplex emission exhibits concentration dependence. At that time we were not able to prepare high molecular weight samples because of the synthetic difficulty. 

When DP exceed a threshold value, the efficiency of interpolymer association starts to decrease. The high molecular weight polymer would be more entangled so that effective polymer surface for interaction decreases. Indeed we found that the interpolymer association developed smoothly upto a high concentration in good solvents but not in poor solvents. The features of interpolymer association are sketched schematically in Fig. 5. The same trend of the molecular weight dependent interpolymer association was observed for J[6 as well. The optimum DP for interpolymer association is, however, much larger than that of... 

The concentration dependent exciplex emission does not necessarily run parallel to the tendency of the interpolymer association in the ground state. Another explanation based on the enhancement of interpolymer association after photoexcitation would be, however, unacceptable. The diffusion constant of polymer molecules and consequently, the rate of polymer association should decrease with increasing DP while the rate has to compete with the decay rate of the singlet excited state. The observed DP dependent interpolymer... 

The absolute degree of interpolymer association cannot be, however, estimated from the value of Fg/Fm. As the extensive studies on solvent effects on exciplex lifetime and emission efficiency indicate (16), the exciplex emission intensity under the stationary excitation condition decreases with increasing the solvent polarity because of decreases in both the exciplex lifetime and the emission probability. 

The finding that the optimum DP for interpolymer association is smaller in a poor solvent than that in a good solvent is in good agreement with the preceding discussions. We observed the same trend for 16, as well. 

Hydrophobic associations in random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate and some methacrylamides and methacrylates substituted with bulky hydrophobes are described with a focus on preferential intrapolymer self-association which leads to the formation of single-macromolecular assemblies (i.e., unimolecular micelles). Structural parameters that critically determine the type of the macromolecular association (i.e., intra- vs. interpolymer associations) are discussed, which include the type of hydrophobes, their content in a polymer, sequence distribution of electrolyte and hydrophobic monomer units, and the type of spacer bonding. Functionalization of single-macromolecular assemblies with some photoactive chromophores is also presented. 

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