Poly apolar solvents

In order to keep polyamides soluble in relatively apolar solvents, the use of flexible (macro)monomers such as a, co-(diaminopropyl)polydimethylsiloxane [52] or oligoethyleneglycol-based diamines [53, 54] has been proven to be a successful approach (Fig. 10). Poly condensations of dimethyl adipate with a variety of diamines were successful in bulk and at moderate temperatures between 60 and 100 °C (reaction A in Fig. 10). The low temperatures (60-100 °C) that suffice in these polymerizations also allow the use of monomers that are thermally instable, such as diethyl fumarate [53]. Moreover, multifunctional amines could be regioselectively polymerized up to molecular weights of 9 kDa, making lipase catalysts a valuable tool for the preparation of well-defined polyamides that can be further functionalized with active groups. 

Rebourt et al. prepared crosslinked poly(3-octylthio-phene) by copolymerizing 3-octylthiophene with trithienylbenzene [169]. The coplymers with a high level of crosslinking points (30%) swelled in apolar solvents and could be doped with iron(III) chloride. Poly(trithienylbenzene) neither swelled nor could be doped. 

Ref, 19, 20) are well worth describing here in some detail, as they focus on the choice of a phase transfer catalyst and on several other factors which are of importance in the chemical modification of soluble poly(chloromethy1 styrene). In a first series of experiments involving solid-liquid reactions with potassium acetate as a nucleophile, Nishikubo and coworkers observe that while reactions carried out without any added phase transfer catalyst do not work in apolar solvents, satisfactory results can be obtained in DMF (Table 1) this confirms previous observations (Ref. 7, 14, 23, 24) which suggest that DMF and DMSO are excellent solvents for nucleophilic displacements on poly(chloromethyl styrene). 

Hyperbranched poly(aryl ether oxindole)s (hb-PAE-Oxns) with a DB of 100% were prepared by Fu et al. [176] from an isatin-based AB2 monomer (1—36, Scheme 12) by one-pot polymerization without using toxic organometaUics nor chromatographic purification. The hb-PAE-Oxns soluble in apolar solvents were able to encapsulate a hydrophilic dye from the same polymer. 

Freudenberger,. C Spiteller, P., Bauer, R Kessler, H Luy, B. Stretched poly(dimethylsiloxane) gels as NMR alignment media for apolar and weakly polar organic solvents an ideal tool for measuring RDCs at low molecular concentrations. /. Am. Chem. Soc. 2004, 326, 14690-14691. 

Polymers of 4(5)-vinylimidazole and copolymers containing this monomer are usually studied with ethanol-buffer mixtures as solvent because of their insolubility in water. Overberger and Smith (82) found that poly(l-Me-5-vinylimidazole) was soluble in water. Negatively charged substrates with long apolar side chains were bound very strongly to this polymer. A rate enhancement of 106 over the monomeric analog, 1,5-dimethylimidazole, was observed. 

As depicted in Fig. 5a, the diblock copolymer polystyrene-bfock-poly (2-vinylpyridine) (PS- -P2VP), consisting of a hydrophobic apolar PS block attached to a hydrophilic polar P2VP domain, is widely used to prepare ordered monolayers of inorganic nano-objects. The solubilisation of PS- -P2VP in toluene leads to the formation of homodisperse reverse micelles made of a hydrophilic P2VP core and a hydrophobic PS outer shell interacting with the solvent molecules. 

Many macromolecular eompounds dissolve in mixtures better than in pure solvents [20]. Thus, poly (vinyl ehloride) is insoluble in acetone as well as in carbon disulfide, but soluble in a mixture of the two. The opposite situation is also known. Malono-nitrile and A, A -dimethylformamide both dissolve polyacrylonitrile but a mixture of the two does not [20]. Soaps dissolve neither in ethylene glycol nor in hydrocarbons at room temperature but are quite soluble in a mixture of the two. Here, ethylene glycol solvates the ionie end, and the hydrocarbon the apolar end of the fatty acid chain [128]. 

Recently, we are also able to perform liquid-liquid extractions of water-soluble dyes from water to organic solvents like toluene using the unimolecular dendritic micelles as extractants. These guest-host properties of the modified poly(propylene imine) dendrimers make use of the basic nature of the interior of the dendrimer. Therefore, it is possible to transfer dyes like Bengal Rose into toluene. Although simple tri-octylamines are capable of transferring these dyes as well, it is evident from the experiments that unimolecular dendritic inverted micelles are much more selective, probably due to the shielding effect of the apolar shell [70]. 

Freudenherger, J. C. Spiteller, P. Baure, R. Kessler, H. Luy, B., Stretched Poly(dimethylsiloxane) Gels as NMR Alignment Media for Apolar and Weakly Polar Organic Solvents An Ideal Tool for Measuring RDCs at Low Molecular Concentrataions. J.Am. Chem. Soc. 2003,126,14690-14691. 

Apparently, because of the (necessarily) poor solubility of the dye in the organic solvent, the dye-endgroup ion-pair must be formed in the water-solvent interface. Because of the apolar nature of polystyrene, few endgroups actually come to this interface and, therefore, the ion-pair formation is not quantitative. As the polymer-polymer interaction increases at higher concentrations, the extent of ion-pair formation decreases. This explanation was confirmed recently by experiments of Huber and Thies (13) on the adsorption of toluene-soluble polymers at the toluene-water interface. They conclude that polystyrene has little affinity for this interface but that poly(methyl methacrylate) adsorbs significantly... 

The shrinkage of the polymer chains at low and high ethanol compositions is attributed to increased hydrophobic interactions and hydrogen bonding, respectively. Poly(l-methyl-5-vinylimidazole) in a solvent of low ethanol content is similarly in a tightly coiled conformation due to an increased hydrophobic interaction. This shrinkage in polymer conformation has been attributed by us to the apolar nature of the polymer s hydrocarbon backbone. 

---