Hydrophilic polymers long chains

Currently available BAS include cholestyramine, colestipol and colesevelam hydrochloride (colestimide). Cholestyramine comprises a long-chain polymer of styrene with divinylbenzene trimethylbenzylammonium groups, whereas colestipol is a long-chain polymer of l-chloro-2,3-epoxypropane with diethylenetriamine. Colesevelam HCl is poly(allylamine hydrochloride) cross-linked with epichlorohydrin and alkylated with 1-bromodecane and 6-bromo-hexyl-trimethylammonium bromide. Bile-acid binding is enhanced and stabilised in the latter compound by long hydrophobic sidechains, increased density of primary amines, and quaternary amine sidechains. For this reason, colesevelam HCl exhibits increased affinity, specificity and capacity to bind bile acids compared with the other BAS. Colesevelam HCl also binds dihydroxy and trihydroxy bile acids with equal affinity, contrasting with cholestyramine and colestipol that preferentially bind dihydroxy bile acids (CDCA and deoxycholic acid). The latter BAS can lead to an imbalance towards trihydroxy bile acids and a more hydrophilic bile-acid pool. 

Figure 5.10. (a) A long chain pyrrole. (6) A polypyrrole. The pyrrole groups have a dipole moment and are hence hydrophilic. Alternation of the direction in which the pyrrole and long chain pyrrole groups are oriented allows the polymer chain to reside at the air/water interface without straining the structure. 

The process is the same as for the normal block co-polymers the hydrophilic block is first made by adding ethylene oxide to ethylene glycol in the normal conditions to produce a sufficiently long chain molecule which is then capped with propylene oxide to produce the hydrophobic blocks. A similar but less extensive series is available offering an even broader selection of surfactant properties from this type of chemistry. 

The present method consists of three steps as illustrated in Scheme 1. In the first step, monolayer films of polyamic acid long chain alkyl-amine salts 4 at the air-water interface are prepared.(9) Unexpectedly, the polyamic acid 3 itself, which possess hydrophilic carboxyl functions in the polymer backbone, did not afford a stable monolayer at the air-water interface. Introduction of a hydrophobic long alkyl chain into 3 was performed by mixing polyamic acids and longchain alkylamines. Polyamic acid salts 4, thus obtained, afforded very stable monolayer films at the air-water interface. In the second step,(10) the polyamic acid salt monolayer films are successfully deposited on appropriate plates such as glass, quartz, or silicon wafer. Finally polyimide multilayer films are obtained by treatment of polyamic acid salt multilayer films on the plates with a mixture of acetic anhydride and pyridine. 

Fig. 12 Shown on the left is a cut through an initial configuration of a vesicle loaded with polymer chains. The hydrophobic and hydrophilic segments of the amphiphile and the hydrophilic beads of the polymer load are shown in red, green, and blue, respectively. Three characteristic snapshots of a rupturing polymersome, loaded with nh = 10 long hydrophilic polymers are shown on the right...

---