Polypropylene oxide core

The nonionic triblock copolymer polyethylene oxide-polypropylene oxide polyethylene oxide (PEO-PPO-PEO) has been widely used in medicine and has shown low toxicity. Wanka et al. [91] studied aggregation behavior of PEO-PPO-PEO polymeric micelles. In this study, the hydrophobic core of this micellar system consisted of dehydrated poly(oxy-propylene) groups which were surrounded by an outer shell of hydrated poly(oxyethylene) groups. The feasibility of using PEO-PPO PEO micelles as a topical ocular carrier for gene delivery was addressed in an in vivo study on nude mice and albino rabbits [92], Each animal eye was treated with a topical application (10 pL for mouse and 50 pL for rabbit) of 0.08 mg/mL of plasmid and 0.3% (w/v) PEO-PPO-PEO polymeric micelles. After 2 days of three times per day topical delivery, the reporter expression was detected in the treated eyes... 

The phase transition between micellar phases of polyethylene oxide-polypropylene oxide-polyethylene oxide) (PEO-PPO-PEO) triblock copolymer in aqueous solution was investigated as a function of temperature using FTIR spectroscopy. As the temperature increases, PO blocks appear to be stretched conformers with strong interchain interactions, and the formation of a hydrophobic core in the micellar phase. The EO chains are found to change to a more disordered structure with low-chain packing density. Both the EO and PO blocks exhibit dehydration during the phase ttansition (78). 

Further examples of polymers used to solubilise hydrophobic compounds are polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock-type copolymers. Such polymers form micelles in solution with the more hydrophobic PPO chains forming the iimer core and the more hydrophilic PEO chains the outer shell. Hydrophobic materials are able to dissolve within the core of the micelles and such systems are finding increasing... 

The modification of the chemical composition of polymer surfaces, and thus their wettability with chemical substances, can be realized in different ways electric discharges more commonly called Corona effect, oxidation by a flame, plasma treatment, UV irradiation and also UV irradiation under ozone atmosphere. Numerous studies have been devoted to the effects of these different treatments. More recently, Strobel et al. [204] compared the effects of these treatments on polypropylene and polyethylene terephthalate using analytical methods such as E.S.C.A., F.T.I.R., and contact angle measurements. They demonstrated that a flame oxidizes polymers only superficially (2-3 nm) whereas treatment realized by plasma effect or Corona effect permits one to work deeply in the polymer (10 nm). The combination of UV irradiation with ozone flux modifies the chemical composition of the polymers to a depth much greater than 10 nm, introducing oxygenated functions into the core of the polymer. 

---