A fundamental investigation of the influence of novel phosphonium bromide salts within the polymer main chain (23.75 mol %) of polyurethanes was conducted to elucidate the effect of ionic associations on hard segment hydrogen bonding. A novel poly(tetramethylene oxide) (PTMO)-based polyurethane containing a phosphonium diol chain extender was prepared using a conventional prepolymer method. In addition, a polyurethane containing a 1,4-butanediol chain extender was synthesized for comparison with the thermomechanical and morphological properties of the phosphonium ion-containing analog. Moreover, the unprecedented comparison of morphological development in the presence of cationic sites is described herein. Differential scanning calorimetry (DSC) revealed that phosphonium polyurethane was more crystalline compared to the noncharged analog, and it was presumed that enhanced hydrogen bonding in the noncharged polyurethane restricted polymer mobility and reduced PTMO crystallinity. Moreover, FT-IR spectroscopy demonstrated that hydrogen-bonding interactions were significantly reduced in the presence of phosphonium cations. These results correlated well with tensile properties, i.e., the noncharged polyurethane offered superior tensile strength compared to phosphonium polyurethane. X-ray scattering indicated that both polyurethanes were amorphous at room temperature and exhibited hard segment microphase separation. Upon stretching, the interparticle scattering between the microphase-separated domains aligned preferentially along the stretching direction. Scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) in the STEM indicated that the charged polyurethane exhibited ionic aggregates that were rich in P and Br.

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Cationic aliphatic ammonium polyionenes, specifically 12,12- and 6,12-ionenes, were synthesized using step-growth polymerization and aqueous-based size exclusion chromatography (SEC) coupled with multiangle laser light scattering (MALLS) revealed absolute molecular weight information. The chromatographic separation of cationic polyelectrolytes presents many additional challenges compared to SEC of nonassociating, neutral polymers. Therefore, an aqueous-based SEC-MALLS mobile phase composition was identified to separate these notoriously challenging polyelectrolytes in an effort to achieve absolute molecular weight analysis. Various solvent compositions were evaluated for their ability to solvate and reproducibly separate both 6,12- and 12,-12-ionenes. Dynamic light scattering (DLS) verified the absence of aggregation of polyionenes in preferred mobile phase compositions. The optimum solvent composition comprised a ternary mixture of 54/23/23 water/methanol/glacial acetic acid, 0.54 M NaOAc, at a pH of 4.0. Weight-average molecular weights for the synthesized ammonium 12,12-ionenes ranged from 11 000 to 40 000 g/mol, and ammonium 6,12-ionenes had weight-average molecular weights ranging from 19 000 to 49 900 g/mol. Mark−Houwink parameters were also determined for both the 12,12- and 6,12-ionenes in the optimum mobile phase using an online capillary viscometer.

Water-soluble 12,12-ammonium ionenes were prepared via the Menschutkin reaction from 1,12-dibromododecane and 1,12-bis(N,N-dimethylamino)dodecane. A stoichiometric imbalance of monomers controlled the final molecular weights of the polymers. The absolute molecular weights were determined for the first time using an online multiangle laser light scattering (MALLS) detector in aqueous size exclusion chromatography (SEC). Weight-average molecular weights ranged from 4300 to 20 900 g/mol. Relationships between weight-average molecular weight and mechanical properties were established for a series of 12,12-ammonium ionenes using both tensile testing and dynamic mechanical analysis (DMA). Tensile analysis of the higher molecular weight ionenes revealed an average tensile strength of 20 MPa and elongations ranging from 230 to 440%. Dissociation of ionic aggregates was observed at 85−88 °C in DMA experiments, and the glass transition temperatures increased with increasing molecular weight (61−88 °C). X-ray scattering revealed an amorphous polyethylene peak at ≈14 nm−1 and a sharp ionic group correlation peak at 4.38 nm−1. These correlations agreed well with the proposed macromolecular structure.

SPONSOR/MONITOR'S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND A SPONSOR/MONITOR'S REPORT NUMBER(S) DDRESS(ES) DISTRIBUTION/AVAILABILITY STATEMENTAppr ed for public release; distribution is unlimited. ov Self-assembly processes and subsequent photo-cross-linking were used to generate cross-linked, ordered microporous structures on the of well defined four-arm star-shaped poly(D,L-lactide) (PDLLA) thin films. The four-arm star-shaped PDLLAs were synthesized using a humid environment, and upon solvent evaporation ns between molar mass, polymer solution viscosity, and pore dimensions were established. The average pore dimension decreased with increasing polym ution concentration, and a linear relationship was observed between relative humidity and average pore dimensions. Highl rdered microporous structures were also developed on four-arm star-shaped methacrylate-modified PDLLA (PDLLA-UM) t in films. Subsequent photo-cross-linking resulted in more stable PDLLA porous films. The photo-cross-linked films were insoluble, and the honeycomb structures were retained despite solvent exposure. Free-standing, structured PDLLA-UM thin f s were obtained upon drying for 24 h. Ordered microporous films based on biocompatible and biodegradable polym h as PDLLA, offer potential applications in biosensing and biomedical applications. ReceiVed January 31, 2006. In Final Form: July 31, 2006 Self-assembly processes and subsequent photo-cross-linking were used to generate cross-linked, ordered microporous structures on the surfaces of well defined four-arm star-shaped poly(D,L-lactide) (PDLLA) thin films. The four-arm star-shaped PDLLAs were synthesized using an ethoxylated pentaerythritol initiator. Solutions of the PDLLAs were cast in a humid environment, and upon solvent evaporation, ordered honeycomb structures (or breath figures) were obtained. Correlations between molar mass, polymer solution viscosity, and pore dimensions were established. The average pore dimension decreased with increasing polymer solution concentration, and a linear relationship was observed between relative humidity and average pore dimensions. Highly ordered microporous structures were also developed on four-arm star-shaped methacrylate-modified PDLLA (PDLLA-UM) thin films. Subsequent photocross-linking resulted in more stable PDLLA porous films. The photo-cross-linked films were insoluble, and the honeycomb structures were retained despite solvent exposure. Free-standing, structured PDLLA-UM thin films were obtained upon drying for 24 h. Ordered microporous films based on biocompatible and biodegradable polymers, such as PDLLA, offer potential applications in biosensing and biomedical applications. SUPPLEMENTARY NOTES

Functional oligomers based on glutathione (GSH) and poly(ethylene glycol) diacrylate (PEGDA) were synthesized via Michael addition. Well-defined, spherical nanoparticle self-assembly was confirmed via dynamic light scattering and transmission electron microscopy. In addition, a series of Michael addition oligomers containing GSH were prepared with various molecular weights of poly(ethylene glycol) (PEG). Thermal analysis indicated that the oligomers were thermally stable to approximately 160 degrees C, and the Tg increased as the PEG molecular weight increased. In addition, thiol-terminated PEG was synthesized and reacted with GSH to form disulfide-linked oligomers to probe potential antioxidant therapies. SH-SY5Y cells were utilized in cell culture experiments, and hydrogen peroxide induced oxidative stress on the cells. Disulfide-linked GSH oligomers were 100% effective at protecting SH-SY5Y cells from oxidative stress, whereas the Michael addition GSH oligomers did not offer protection.

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Covalently crosslinked networks based on poly(propylene glycol) bis(acetoacetate) with either neopentyl glycol diacrylate or hydroxyethyl acrylate derivatized bis(4‐isocyanatocyclohexyl)methane (HMDI) were prepared utilizing the Michael addition reaction in the presence of catalytic quantities of diazabicyclo[5.4.0]undec‐7‐ene (DBU). These networks were prepared in the absence of solvent at 23 °C without the formation of byproducts. Mechanical and thermal analyses of the networks were performed utilizing DMA, tensile testing, and TGA. Tensile analysis revealed that the introduction of hydrogen‐bonding urethane linkages in the diacrylate segment resulted in higher tensile strengths and elongation to break compared with nonhydrogen‐bonding analogs. All crosslinked products exhibited high gel fractions and excellent thermomechanical properties. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4118–4128, 2007