The induced circular dichroism (ICD) of several chiral nitrosamines and various chiral reagents has been investigated. The interaction is attributed to a 1:1 hydrogen bonded complex between the NO group of the nitrosamine and the hydroxyl groups of alcohols and polyols, or the amino group of amines. Only those chiral reagents possessing large differences in size of the groups about the hydrogen bonding site contributed to CD anomalies. The acyclic 2-octanols did not give observable Cotton effects, presumably due to the similarity in size of the methyl and methylene groups and rotational freedom of the acyclic system. The signs of the Cotton effects could be correlated with the absolute configuration of the sterically hindered alcohols and amines. Only the alpha, axial hydrogens of conformationally biased, heterocyclic nitrosamines were found to undergo selective hydrogen-deuterium exchange, suggesting that this feature is critical for nitrosamine carcinogenicity.

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Low molecular weight liquid polybutadienes (1000 – 2000 g/mol) consisting of 60 mol% 1,2-polybutadiene repeating units were synthesized via anionic telomerization and conventional anionic polymerization. Maintaining the initiation and reaction temperature less than 70 °C minimized chain transfer and enabled the telomerization to occur in a living fashion, which resulted in well-controlled molecular weights and narrow polydispersity indices. MALDI-TOF mass spectrometry confirmed that the liquid polybutadienes synthesized via anionic telomerization contained one benzyl end and one protonated end. Subsequently, 2-ureido-4[1H]-pyrimidone (UPy) quadruple hydrogen-bonding was introduced to telechelic poly(ethylene-co-propylene), and mechanical characterization of the composites with UPy-functionalized carbon nanotubes was performed. The composites enhanced the mechanical properties and the UPy-UPy association between the matrix polymer and carbon nanotubes prevented the decrease of an elongation at break. The matrix polymer was also reinforced without sacrificing the processability. Additionally, UPy groups were introduced to styrene-butadiene rubbers (SBRs). Introducing UPy groups to SBRs drastically changed the physical properties of these materials. Specifically, the SCMHB networks served as mechanically effective crosslinks, which raised Tg and enhanced the mechanical performance of the SBRs. Novel site-specific sulfonated graft copolymers, poly(methyl methacrylate)-g-(poly(sulfonic acid styrene)-b-poly(tert-butyl styrene)), poly(methyl methacrylate)-g-(poly(tert-butyl styrene)-b-poly(sulfonic acid styrene)), and the corresponding sodium sulfonate salts were successfully synthesized via living anionic polymerization, free radical graft copolymerization, and post-sulfonation strategies. The graft copolymers contained approximately 9 – 10 branches on average and 4 wt% of sulfonic acid or sodium sulfonate blocks adjacent to the backbone or at the branch terminus. The mobility of the sulfonated blocks located at the branch termini enabled the sulfonated blocks to more readily interact and form ionic aggregates. The glass transition temperatures (Tg) of the sulfonated graft copolymers with sulfonated blocks at the branch termini were higher than that of copolymers with sulfonated blocks adjacent to the backbone. More facile aggregation of sulfonated blocks at the branch termini resulted in the appearance of ionomer peaks in SAXS whereas ionomer peaks were not observed in sulfonated graft copolymers with sulfonated blocks adjacent to the backbone. In addition, similar analogues, novel site-specific sulfonated graft copolymers, poly(methyl methacrylate)-g-(poly(sulfonic acid styrene)-b-poly(ethylene-co-propylene)) (PMMA-g-SPS-b-PEP), poly(methyl methacrylate)-g-(poly(ethylene-co-propylene)-b-poly(sulfonic acid styrene)) (PMMA-g-PEP-b-SPS), and the corresponding sodium sulfonate salts were successfully synthesized. Estimated ï £N values predicted the phase separation of each block and differential scanning calorimetry (DSC) and dynamic mechanical analysis confirmed the phase separation of each block component of the graft copolymers. The aggregation of sulfonic acid or sodium sulfonate groups at the branch termini restricted the glass transition of the PEP block. This lack of the glass transition of the PEP block resulted in higher storage modulus than a sulfonated graft copolymer with sulfonated blocks adjacent to the backbone. The location of sulfonated blocks in both sulfonic acid and sodium sulfonate graft copolymers significantly affected the thermal, mechanical and morphological properties. Lastly, symmetric (16000 g/mol for each block) and asymmetric (14000 g/mol and 10000 g/mol for each block) poly(ethylene-co-propylene)-b-poly(dimehtylsiloxane) (PEP-b-PDMS) were synthesized using living anionic polymerization and subsequent hydrogenation. The onset of thermal degradation for the PEP-b-PDMS diblock copolymer was higher than 300 ºC and PEP-b-PDMS was more thermally stable than the precursor diblock copolymer, polyisoprene-b-PDMS. DSC analysis of PEP-b-PDMS provided Tg of PDMS -125 ºC, Tg of PEP -60 ºC, Tc of PDMS -90 ºC, and Tm of PDMS -46 and -38 ºC, respectively. Appearance of thermal transitions of each PEP and PDMS block revealed the formation of phase separation. Estimated Ï N also supported the phase separation. / Ph. D.

The foundational studies of this dissertation concern the characterization of segmented polyurethanes and polyureas synthesized without the use of chain extenders'molecules that are typically used to promote a microphase separated morphology that gives these materials their useful characteristics. Polyurethanes in which a single asymmetric diisocyanate comprising the whole of the hard segment were found to display poor microphase separation. Conversely, polyurethanes in which a single symmetric diisocyanate composed the hard segment were found to display good microphase separation. The more efficient packing of the symmetric hard segments also led to an increase in hard segment connectivity and hence higher values of storage moduli in these systems. When hydroxyl-terminated diisocyanates were replaced with amine-terminated diisocyanates, polyureas were formed. Here too, diisocyanate symmetry was found to play a key role with symmetric diisocyanates leading to better microphase separation. In addition, the polyurea materials displayed broader service temperature windows than their polyurethane counterparts as the relatively stronger bidentate hydrogen bonding replaced monodentate hydrogen bonding in these materials. A thread-like, microphase separated morphology was visually confirmed using atomic force microscopy. Other techniques such as ambient temperature tensile testing, and wide and small angle x-ray scattering were employed to confirm the presence of the microphase separated structure. The investigation into the effects of diisocyanate chemistry and its symmetry was broadened to incorporate non-chain extended polyurethane materials with different soft segment molecular weights, as well as polyurethanes that did contain chain extenders. Once again the effect of using symmetric versus asymmetric diisocyanates was evident in the structure–property behavior of these systems, with symmetric diisocyanates forming materials that displayed better microphase separation and more connectivity of their hard domains. Lastly, in a departure from the segmented copolymer area, a study was conducted into the influence of casting variables on the solid-state structure of synthetic polypeptide films based on glutamate chemistry. The effect of solvent evaporation was determined to play a key role in the morphology of these polypeptide films. Measured small angle light scattering patterns were compared to computer calculated patterns to reveal information about the structure, shape, and length scale of the polypeptide structure. / Ph. D.

The synthesis of a variety of novel functionalized polymers using living polymerization techniques to achieve functional and stimuli responsive coatings on silica surfaces are described. Since microscopic features on a surface influence the overall wetting properties of the surface, a systematic investigation of the influence of polymer architecture on the microscopic characteristics of the modified surfaces was studied using silane-functionalized linear and novel star-branched polystyrene (PS). Star-branched modifiers provide functional and relatively well-defined model systems for probing surface properties compared to ill-defined highly branched systems and synthetically challenging dendrimers. Using these simple star-shaped macromolecules it was shown that the topographies of the polymer-modified surfaces were indeed influenced by the polymer architecture. A model explaining the observed surface features was proposed. A living polymerization strategy was also used to synthesize centrally functionalized amphiphilic triblock copolymers. The amphiphilic copolymers exhibited stimuli responsive changes in surface hydrophobicity. In spite of multiple solvent exposures, the copolymer films remained stable on the surface indicating that the observed changes in surface properties were due to selective solvent induced reversible rearrangement of the copolymer blocks. The chemical composition of the copolymers was tailored in order to tune the response time of the surface anchored polymer chains. Thus, the polymer coatings were used to reversibly change the surface polarities in an on-demand fashion and could find possible applications as smart adhesives, sensors and reusable membrane devices. In contrast to the afore-mentioned covalent modification approach, which often leads to permanent modification of surfaces, renewable surfaces exhibiting "universal" adhesion properties were also obtained through non-covalent modification. By employing hydrogen bonding interactions between DNA bases, surfaces functionalized with adenine groups were found to reversibly associate with thymine-functionalized polymers. This study describing the solvato-reversible polymer coating was the first demonstration on silica surfaces. A systematic investigation of the influence of surface concentration of the multiple hydrogen bonding groups and their structure on the extent of polymer recognition by the modified surfaces is also discussed. / Ph. D.

Bio-inspired monomers functionalized with nucleobase or ionic group allowed synthesis of supramolecular polymers using free radical polymerization and controlled radical polymerization techniques. Comprehensive investigations for the structure-property-morphology relationships of these supramolecular polymers elucidated the effect of noncovalent interactions on polymer physical properties and self-assembly behaviors. Reverse addition-fragmentation chain transfer (RAFT) polymerization afforded acrylic ABC and ABA triblock copolymers with nucleobase-functionalized external blocks and a low-Tg central block. The hard-soft-hard triblock polymer architecture drove microphase-separation into a physically crosslinked hard phase in a low Tg matrix. Hydrogen bonding in the hard phase enhanced the mechanical strength and maintained processability of microphase-separated copolymers for thermoplastics and elastomers. A thermodynamically favored one-to-one stoichiometry of adenine and thymine yielded the optimal thermomechanical performance. Intermolecular hydrogen bonding of two thymine units and one adenine unit allowed the formation of base triplets and directed self-assembly of ABC triblock copolymers into remarkably well-defined lamellae with long-range ordering. Acetyl protected cytosine and guanine-containing random copolymers exhibited tunable cohesive strength and peel strength as pressure sensitive adhesives. Post-functionalization converted unprotected cytosine pendent groups in acrylic random copolymers to ureido-cytosine units that formed quadruple self-hydrogen bonding. Ureido-cytosine containing random copolymers self-assembled into nano-fibrillar hard domains in a soft acrylic matrix, and exhibited enhanced cohesive strength, wide service temperature window, and low moisture uptake as soft adhesives. A library of styrenic DABCO salt-containing monomers allowed the synthesis of random ionomers with two quaternized nitrogen cations on each ionic pendant group. Thermomechanical, morphological, and rheological analyses revealed that doubly-charged DABCO salts formed stronger ionic association and promoted more well-defined microphase-separation compared to singly-charged analogs with the same charge density. Bulkier counterions led to enhanced thermal stability, increased phase-mixing, and reduced water uptake for DABCO salt-containing copolymers, while alkyl substituent lengths only significantly affected water uptake of DABCO salt-containing copolymers. Step growth polymerization of plant oil-based AB monomer and diamines enabled the synthesis of unprecedented isocyanate-free poly(amide hydroxyurethane)s, the first examples of film-forming, linear isocyanate-free polyurethanes with mechanical integrity and processability. Successful electrospinning of segmented PAHUs afforded randomly orientated, semicrystalline fibers that formed stretchable, free-standing fiber mats with superior cell adhesion and biocompatibility. / Ph. D.

Advanced analytical techniques were utilized to investigate the intermolecular forces in several nanostructured materials. Techniques including, but not limited to, isothermal titration calorimetry (ITC), variable temperature Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-Vis) thermal curves were used to study the fundamental interactions present in various nanomaterials, and to further probe the influence of these interactions on the overall behavior of the material. The areas of focus included self-assembly of surfactant micelles, polycation complexation of DNA, and temperature-dependent hydrogen bonding in polymeric systems. ITC was successfully used to determine the low critical micelle concentration (CMC) for a novel gemini surfactant with limited water solubility. CMCs were measured at decreasing methanol molar fractions (xMeOH) in water and the resulting linear relationship between CMC and methanol concentration was used to mathematically extrapolate to a predicted CMC at xMeOH = 0. Using this technique, the CMC value for the novel gemini surfactant was predicted to be 0.037 ± 0.004 mM. This extrapolation technique was also validated with surfactant standards. ITC was also used to investigate the binding thermodynamics of polyplex formation with polycations and DNA. The imidazolium-containing and trehalose-based polycations were both found to have endothermic, entropically driven binding with DNA, while the adenine-containing polycation exhibited exothermic DNA binding. In addition, ITC was also used to confirm the stoichiometric binding ratio of linear polyethylenimine and DNA polyplexes as determined by a novel NMR method. Dynamic light scattering (DLS) and zeta potential measurements were also performed to determine the size and surface charge of polyplexes. Circular dichroism (CD) and FTIR spectroscopies provided information regarding the structural changes that may occur in the DNA upon complexation with polymers. UV-Vis thermal curves indicated that polyplexes exhibit a greater thermal stability than DNA by itself. Variable temperature FTIR spectroscopy was used to quantitatively compare the hydrogen bonding behavior of multi-walled carbon nanotube (MWCNT)-polyurethane composites. Spectra were collected from 35 to 185 deg C for samples containing various weight percent loadings of MWCNTs with different hydrogen bonding surface functionalities. Peak fitting analysis was performed in the carbonyl-stretching region for each sample, and the hydrogen-bonding index (Rindex) was reported. Rindex values were used to quantitatively compare all of the composite samples in regards to temperature effects, weight percent loadings of MWCNTs, and the different functionalizations. In general, higher weight percent loadings of the MWCNTs resulted in greater Rindex values and increased hydrogen bond dissociation temperatures. In addition, at 5 and 10 wt% loadings the initial Rindex values displayed a trend that tracked well with the increasing hydrogen bonding capacity of the various surface functionalities. / Ph. D.

Palladium(II) acetate and palladium(II) chloride react with amino acids in acetone/water to yield cis or trans square planar bis-chelated palladium amino acid complexes. The naturally occurring amino acids and some N-alkylated and substituted derivatives and homologs were evaluated as ligands. Thirty-eight amino acids in total were investigated as ligands. The formation of aquo complexes in water was observed and studied by 13C NMR spectroscopy and modeled by DFT calculations. Each class of amino acid ligand is catalytically active with respect to the oxidative coupling of olefins and phenylboronic acids. Some enantioselectivity is observed and the formation of products not reported in other Pd(II) oxidative couplings is seen. Both activated and non-activated alkenes were oxidatively coupled to phenylboronic acids incorporating both electron-donating and electron-withdrawing groups. The crystal structures of nineteen catalyst complexes were obtained. The extended lattice structures arise from N-H..O or O..(HOH)..O hydrogen bonding. NMR, HRMS, FTIR, single crystal XRD, and powder XRD data are evaluated. / Ph. D.