Polyethylene oxide triblock copolymers

Fig. 22 Images and data representing development and application of DLS on a chip a one iteration in the design of a microfluidic DLS fabricated from aluminum with the surface anodized black to reduce surface reflections b image of a microfluidic chip that integrates polymer synthesis with DLS. The machined channels have been covered by a Kapton sheet fixed with adhesive c data for temperature depended micelle formation of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (Pluronic P85) at 2% by volume in water. (Derived from [106] with permission)...

Habas and co-workers [43] carried out an investigation into the viscoelastic properties of aqueous solutions of a four-branched polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer in the unimer range using TMA, DMTA and small-angle neutron scattering. The aqueous solutions were characterised in the crystalline phase and a modified version of Eyring s theory was used to describe the stress-time dependence of ordered solutions. 

A triblock copolymer, Pluronic F-68, (polyethylene oxide-polypropylene oxide- polyethylene oxide triblock copolymer), a synthetic surfactant [74] was adsorbed to hydrophobic substrata such as PDMS to form low-density polymer brush-coatings [86]. The PEO-PPO-PEO triblock copolymers in many ways exhibit a similar behavior as low molecular weight non-ionic surfactants. The tendency of these amphiphilic polymers to self-assemble in aqueous systems and at interfaces has led to widespread applications for the stabilization of macromolecular colloidal suspensions and for the manipulation of surface properties [92]. Anti-fouling properties of Pluronic copolymers result from the fact that the Pluronic copolymers PPO domain, which... 

Almgren. M., J. Van Stam, C. Lindblad, P. Stilbs, and P. Bahadur. 1991. Aggregation of polyethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers in the presence of sodium dodecyl sulfate in aqueous solutiod.. Phys. Chem. 95 5677-5684. 

Schillen K, Bryskhe K (1999) Vesicles formed from a polyethylene oxide) — polypropylene oxide) — poly(ethylene oxide) triblock copolymer in dilute aqueous solution. Macromolecules 32 6885-6888... 

SBA-15 is prepared under acidic conditions using polyethylene oxide)-poly(propylenc oxide)-poly(elhylene oxide) triblock copolymers, (EO)n(PO)7o(EO)n, as templates, e.g. Pluronic P123 (n = 20), Pluronic L121 (n - 5) or Pluronic F127 (n = 106). In a typical synthesis [54,551 based on the original procedures [33], 4.0 g of (EO)2o(PO)7o(EO)2o copolymer was dissolved in 150 g of 1.6 M HC1. To this solution was added 8.50 g of TEOS, and the resulting mixture was stirred until TEOS was dissolved. The mixture was heated in an oven for 24 h at 308 K. and then 24 h more at 373 K. under static condition. Silica products were filtered, dried (without washing), and calcined at 823 K. 

The above triblocks are not the most efficient emulsifiers or dispersants—the PPO chain is not sufficiently hydrophobic to provide a strong anchor to a hydrophobic surface or to an oil droplet. The surface activity of the PEO-PPO-PEO triblock at the OAV interface is probably due to rejection anchoring the PPO chain is not soluble in water or most oils. Several other di- and triblock copolymers have been synthesized diblocks of polystyrene block-polyvinyl alcohol triblocks of poly(methylmethacrylate)-block polyethylene oxide-poly(methyl methacrylate) diblocks of polystyrene-polyethylene oxide triblocks of polyethelene oxide-polystyrene-polyethylene oxide. 

Gallet and co-workers [45] studied the oxidative thermal degradation of polyethylene oxide-ethylene oxide triblock copolymer. It was found by MALDI that degradation starts after 21 days at 80 °C. 

The phase behavior can additionally be manipulated by adding block-selective solvents (low-molecular-weight solvents or polymers) [51]. A particularly important example is poly(ethylene oxide)-Wock-poly(propylene oxide)-h/ock-poly(ethylene oxide) triblock copolymers in aqueous solvents (selective with respect to polyethylene oxide) [52]. Along a similar line, bicontinuous microemulsions can be achieved in symmetric temaiy blends consisting of diblock copolymers mixed with the two corresponding homopolymers [53]. 

Au NPs have been synthesized in polymeric micelles composed of amphiphilic block copolymers. Poly(styrene)-block-poly(2-vinylpyridine) in toluene has been used as nanocompartments loaded with a defined amount of HAuCl4 and reduced with anhydrous hydrazine. The metal ions can be reduced in such a way that exactly one Au NP is formed in each micelle, where each particle is of equal size between 1 and 15 nm [113]. In another example, the addition of HAuCfi to the triblock copolymer (PS-b-P2VP-b-PEO) (polystyrene-block-poly-2-vinyl pyridine-block-polyethylene oxide) permits the synthesis of Au N Ps using two different routes, such as the reduction of AuC14 by electron irradiation during observation or by addition of an excess of aqueous NaBH4 solution [114]. 

Pharmaceutical research on polymeric micelles has mainly focused on two kinds of block copolymers, namely, AB block copolymers or diblock copolymers and ABA or BAB block copolymers known as triblock copolymers (Bader et al., 1984 Yokoyama et al., 1990,1991 Kwon and Okano, 1996, 1999 Kwon, 1998, 2003 Alakahov and Kabanov, 1998). The most common hydrophilic block (A) of the block copolymers is polyethylene oxide (PEO). This polymer is highly hydrated through hydrogen bonding and sterically stabilizes surfaces of the polymeric micelles in aqueous systems. 

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... 

Graft copolymers of poloxamers and either poly(acrylic acid) or chitosan change from a sol to a gel at temperature above 37 °C. The appearing gel forms a stable matrix that can retain a drag for its sustained release. The triblock copolymer consisting of polyethylene oxide)-poly(/-lactide)-poly(ethylene oxide) (PEO-PLLA-PEO) is also temperature-sensitive but shows an opposite gellation property. At low... 

Microscopic foam films have been used to study the steric interaction between two liquid/gas interfaces [130]. Two ABA triblock copolymers of the Synperonic PE series were employed P85 and F108. These commercial non-ionic surfactant were used as obtained from ICI Surfactants, Witton, UK. Blocks A are hydrophilic polyethylene oxide (PEO) chains, while block B is a hydrophobic polypropylene oxide (PPO) chain. The molecular masses and average EO contents are known from the manufacturer and yield approximate chemical formulae (Table 3.3). Data about the surface tension of electrolyte-free aqueous copolymer solutions can be seen in Fig. 3.31 [130]. It was additionally checked that NaCl (up to 510 2 mol dm 3) had no influence on these values. 

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