Current-induced formation of gradient crystals in block copolymer electrolytes.

Conventional ordered phases such as crystals and liquid crystals have constant domain spacings. In this Letter, we report on the formation of coherently ordered morphologies wherein the domain spacing changes continuously along a specified direction. We have coined the term "gradient crystal" to refer to this structure, a signature of which is a small-angle X-ray scattering pattern that resembles a sundial. Gradient crystals composed of a gyroid morphology form spontaneously when ionic current is driven through a block copolymer electrolyte. We propose that this structure forms because it allows for a continuous change in domain spacing without requiring the introduction of defects. Previous studies have shown that applied electric fields ranging from 1000 to 40,000 V/mm can induce long-range structural order, alignment, and morphological transitions in block copolymers. Gradient crystals form under applied electric fields as low as 2.5 V/mm due to the presence of direct ionic currents that are absent in the aforementioned studies.

The effect of complexation hydrogels on insulin transport in intestinal epithelial cell models.

A novel class of pH-sensitive complexation hydrogels composed of methacrylic acid and functionalized poly(ethylene glycol) (PEG) tethers, referred to as P(MAA-g-EG) WGA, was investigated as an oral protein delivery system. The PEG tethers were functionalized with wheatgerm agglutinin (WGA), a lectin that can bind to carbohydrates in the intestinal mucosa, to improve residence time of the carrier and absorption of the drug at the delivery site. The ability of P(MAA-g-EG) WGA to improve insulin absorption was observed in two different intestinal epithelial models. In Caco-2 cells P(MAA-g-EG) WGA improved insulin permeability 9-fold as compared with an insulin only solution, which was similar to the improvement by P(MAA-g-EG). P(MAA-g-EG) and P(MAA-g-EG) WGA were also evaluated in a mucus-secreting culture that contained Caco-2 and HT29-MTX cells. Insulin permeability was increased 5-fold in the presence of P(MAA-g-EG) and P(MAA-g-EG) WGA. Overall, it is clear that P(MAA-g-EG) WGA enhances insulin absorption and holds great promise as an oral insulin delivery system.

Effect of ion distribution on conductivity of block copolymer electrolytes.

Energy-filtered transmission electron microscopy (EFTEM) was used to determine the distribution of lithium ions in solid polymer electrolytes for lithium batteries. The electrolytes of interest are mixtures of bis(trifluoromethane)sulfonimide lithium salt and symmetric poly(styrene-block-ethylene oxide) copolymers (SEO). In contrast to current solid and liquid electrolytes, the conductivity of SEO/salt mixtures increases with increasing molecular weight of the copolymers. EFTEM results show that the salt is increasingly localized in the middle of the poly(ethylene oxide) (PEO) lamellae as the molecular weight of the copolymers is increased. Calculations of the inhomogeneous local stress field in block copolymer microdomains, modeled using self-consistent field theory, provide a quantitative explanation for this observation. These stresses, which increase with increasing molecular weight, interfere with the ability of PEO chains to coordinate with lithium cations near the walls of the PEO channels where ion mobility is expected to be low.

Rasch analysis of word identification and magnitude estimation scaling responses in measuring naive listeners' judgments of speech intelligibility of children with severe-to-profound hearing impairments.

PURPOSE: Speech intelligibility research typically relies on traditional evidence of reliability and validity. This investigation used Rasch analysis to enhance understanding of the functioning and meaning of scores obtained with 2 commonly used procedures: word identification (WI) and magnitude estimation scaling (MES). METHOD: Narrative samples of children with hearing impairments were used to collect data from listeners with no previous experience listening to or judging intelligibility of speech. WI data were analyzed with the Rasch rating scale model. MES data were examined with Rasch partial credit model when individual scales were unknown, and the Rasch rating scale model was used with reported individual scales. RESULTS: Results indicated that both procedures have high reliability and similar discriminatory power. However, reliability and separation were lower for MES when scales were unknown. Both procedures yielded similar speech sample ordering by their difficulty. However, sampling gaps were noted as well as item misfit issues. CONCLUSIONS: Functioning wise, both WI and MES procedures were highly reliable in measuring speech intelligibility, and measurement precision may be increased by asking participants to report their individual scales when using MES. Meaning wise, operationalization of speech intelligibility did not change when either WI or MES procedure was used. However, the sample selection procedure needs to be further refined to allow for a wider selection of stimuli.

Wheat germ agglutinin functionalized complexation hydrogels for oral insulin delivery.

Insulin was loaded into hydrogel microparticles after two hours with loading efficiencies greater than 70% for both poly(methacrylic acid-grafted-ethylene glycol) (P(MAA-g-EG)) and poly(methacrylic acid-grafted-ethylene glycol) functionalized with wheat germ agglutinin (P(MAA-g-EG) WGA). The pH-responsive release results demonstrated that the pH shift from the stomach to the small intestine can be used as a physiologic trigger to release insulin from P(MAA-g-EG) and P(MAA-g-EG) WGA microparticles, thus limiting release of insulin into the acidic environment of the stomach. Microplates were successfully treated with PGM to create a surface that allowed for specific binding between mucins and lectins. The 1% PGM treatment followed by a 2 h BSA blocking step gave the most consistent results when incubated with F-WGA. In addition, the PGM-treated microplates were shown to create specific interactions between F-WGA and the PGM by use of a competitive carbohydrate. The 1% PGM treated microplates were also used to show that adhesion was improved in the P(MAA-g-EG) WGA microparticles over the P(MAA-g-EG) microparticles. The interaction between the PGM-treated microplate and P(MAA-g-EG) WGA was again shown to be specific by adding a competitive carbohydrate, while the interaction between P(MAA-g-EG) and the PGM-treated microplate was nonspecific. Cellular monolayers were used as another method for demonstrating that the functionalized microparticles increase adhesion over the nonfunctionalized microparticles. This work has focused on improving the mucoadhesive nature of P(MAA-g-EG) by functionalizing these hydrogel carriers with wheat germ agglutinin (WGA) to create a specific mucosal interaction and then evaluating the potential of these carriers as oral insulin delivery systems by in vitro methods. From these studies, it is concluded that the addition of the WGA on the microparticles produces a specific adhesion to carbohydrate-containing surfaces and that P(MAA-g-EG) WGA shows great promise as an oral insulin delivery system.