Phenol-formaldehyde (PF) resole and polymeric diphenylmethane diisocyanate (PMDI) are two commonly used exterior thermosetting adhesives in the wood-based composites industry. There is an interest in combining these two adhesives in order to benefit from their positive attributes while also neutralizing some of the negative ones. Although this novel adhesive system has been reportedly utilized in some limited cases, a fundamental understanding is lacking. This research serves this purpose by investigating some of the important aspects of this novel adhesive system. The adhesive rheological and viscometric properties were investigated with an advanced rheometer. The resole/PMDI blends exhibited non-Newtonian flow behavior. The blend viscosity and stability were dependent on the blend ratio, mixing rate and time. The adhesive penetration into wood was found to be dependent on the blend ratio and correlated with the blend viscosity. By using dynamic mechanical analysis, the blend cure speed was found to increase with the PMDI content. Mode I fracture testing of resole/PMDI hybrid adhesive bonded wood specimens indicated the dependence of bondline fracture energy on the blend ratio. The 75/25 PF/PMDI blend exhibited a high fracture energy with a fast cure speed and processable viscosity. Exposure to water-boil weathering severely deteriorated the fracture energies of the hybrid adhesive bondlines. More detailed chemistry and morphological studies were performed with cross-polarization nuclear magnetic resonance and 13C, 15N-doubly labeled PMDI. A spectral decomposition method was used to obtain information regarding chemical species concentration and relaxation behavior of the contributing components within the major nitrogen resonance. Different urethane concentrations were present in the cured blend bondlines. Water-boil weathering and thermal treatment at elevated temperatures (e.g. > 200°C) caused reduced urethane concentrations in the bondline. Solid-state relaxation parameters revealed a heterogeneous structure in the non-weathered blends. Water boil weathering caused a more uniform relaxation behavior in the blend bondline. By conducting this research, more fundamental information regarding the PF/PMDI hybrid adhesives will become available. This information will aid in the evaluation of, and improve the potential use of PF/PMDI hybrid adhesives for wood-based composites. / Ph. D.

This work addresses the morphology of the wood/ Phenol-Formaldehyde (PF) adhesive interphase using yellow-poplar. In this case, morphology refers to the scale or dimension of adhesive penetration into wood. The objective is to develop methods for revealing ever smaller levels of wood/resin morphology. Dynamic techniques that are commonly utilized in polymer blend studies are investigated as potential methods for probing the wood/ adhesive interphase morphology. These are Dynamic Mechanical Analysis (DMA) and solid state NMR using CP/MAS. PF resin molecular weight is manipulated to promote or inhibit resin penetration in wood, using a very low or a very high molecular weight PF resin. With DMA, the influence of PF resin on wood softening is investigated. It is first demonstrated that the cooperativity analysis according to the Ngai coupling model of relaxation successfully applies to the in-situ lignin glass transition of yellow-poplar and spruce woods. No significant difference in intermolecular coupling is detected between the two woods. It is then demonstrated that combining simple DMA measurements with the cooperativity analysis yields ample sensitivity to the interphase morphology. From simple DMA temperature scans, a low molecular weight PF (PF-Low) does not influence lignin glass transition temperature. However, the Ngai coupling model of relaxation indicates that intermolecular coupling is enhanced with the low molecular weight PF. This behavior is ascribed to the low molecular weight PF penetrating lignin on a nanometer scale and polymerizing in-situ. On the other hand, a high molecular weight resin with a broad distribution of olecular weights (PF-High) lowers lignin glass transition temperature dramatically. This plasticizing effect is ascribed to a small fraction of the PF resin being low enough in molecular weight to penetrate lignin on a nanoscale, but being too dispersed for forming a crosslinked network. With CP/MAS NMR, intermolecular cross-polarization experiments are found unsuitable to probe the angstrom scale morphology of the wood adhesive interphase. However, observing the influence of the PF resins on the spin lattice relaxation time in the rotating frame, HT1r, and the cross-polarization time (TCH) is useful for probing the interphase morphology. None of the resins significantly affects the cross-polarization time, suggesting that angstrom scale penetration does not occur with a low nor a high molecular weight PF resin. However, the low molecular weight PF substantially modifies wood polymer HT1r, indicating that the nanometer scale environment of wood polymers is altered. On the other hand, the high molecular weight PF resin has no effect on wood HT1r. On average, the high molecular weight PF does not penetrate wood on a nanometer scale. Interestingly, the low molecular weight PF resin disrupts the spin coupling that is typical among wood components. Spin coupling between wood components is insensitive to the high molecular weight PF. Finally, it is noteworthy that the two PF resins have significantly different T1r 's in-situ. The low molecular weight resin T1r lies within the range of wood relaxations, suggesting some degree of spin coupling. On the other hand, the T1r of the high molecular weight PF appears outside the range of wood relaxations. Spin coupling between the high molecular weight resin and wood components is therefore inefficient. The CP/MAS NMR and DMA studies converge to identify nanometer scale penetration of the low molecular weight PF in wood. On the other hand, the high molecular weight PF resin forms separate domains from wood, although a very small fraction of the PF-High is able to penetrate wood polymers on a nanoscale. / Ph. D.

This dissertation aims to investigate and correlate structure, dynamics and transport properties of several novel soft materials systems using multiple Nuclear Magnetic Resonance (NMR) methodologies, including solid-state NMR (SSNMR), diffusometry, and imaging, and with the help of X-ray scattering. First, we report the investigation of structure and dynamics of three polymeric membranes: hydroxyalkyl-containing imidazolium homopolymers, poly(arylene ether sulfone) segmented copolymers, and disulfonated poly(arylene ether sulfone) random copolymers using a wide array of SSNMR techniques, including: 1) ¹³C cross-polarization magic angle spinning (CPMAS) with varying cross-polarization (CP) contact time, 2) ¹³C single-pulse magic angle spinning (MAS) with varying delay time, 3) ²³Na single-pulse MAS, 4) two dimensional phaseadjusted spinning sideband (2D PASS), 5) proton spin−lattice relaxation (T₁), 6) rotating frame spin−lattice relaxation (T₁ρ), and 7) center-band-only detection of exchange (CODEX). These various types of SSNMR spectroscopic methods provide a wealth of structural and dynamic information over a wide range of time scales from a few nanoseconds to seconds. We further present a picture of rich structural and transport behaviors in supramolecular assemblies formed by amphiphilic wedge molecules using a combination of ²³Na solid-state NMR, ¹H/²H PFG NMR diffusion, relaxation and grazing-incidence small-angle X-ray scattering. Our results show that the liquid crystalline domains in these materials undergo a transition from columnar to bicontinuous cubic phases with a simple increase in humidity, while the amorphous domain boundaries consist of individual wedge molecules with a significant fraction (~ 10%) of total wedge molecules. Multiple-component diffusion of both wedges and water further confirms the structural and dynamic heterogeneity, with the bicontinous cubic phase being able to facilitate much faster water and ion transport than the columnar phase. We then develop a quantitative approach to probe the migration of two novel “theranostic” polymeric agents (combining “therapeutic” and “diagnostic” functions) into bulk hydrogels using two distinct time-resolved magnetic resonance imaging (MRI) methods. To the best of our knowledge, this is the first work that combines time-resolved MRI experiments to reliably quantify diffusivity of paramagnetic and superparamagnetic nanoparticles in bulk biological media. Our results agree closely with those obtained from fluorescence techniques, yet the capability of our approach allows the analysis of actual nanoparticles diffusion through biogels on mm to cm scales during a range of time periods. Finally, we employ a combination of NMR techniques to obtain a comprehensive understanding of ion clustering and transport behaviors of ionic liquids inside the benchmark ionic polymer Nafion. Spin relaxation shows that anion relaxation is more influenced by the fixed sulfonate groups than cation relaxation. 2D ¹H-¹⁹F heteronuclear Overhauser effect spectroscopy (HOESY) and 1D ¹⁹F¹⁹F selective nuclear Overhauser effect (NOE) spectroscopy confirm our assumption of the formation of ion clusters at low water content in the ionomer. While we observe non-restricted diffusion behavior for cations, anion diffusion is strongly restricted both between domain boundaries and within domains in the absence of water. The restricted anion diffusion can serve as a reliable probe for detailed multiscale structures of the ionomer. / Ph. D.

The objective of this dissertation is to demonstrate different applications of ssNMR, with particular emphasis on uses in polymeric and biosciences. First, dynamics investigations on two polymers will be discussed: (1) disulfonated poly(arylene ether sulfone)s /poly(ethylene glycol) blends (BPS-20_PEG), which are under development as chlorine-resistant reverse osmosis (RO) membrane alternatives to aromatic polyamide (PA) technology, and (2) poly(arylene ether sulfone)s modified with 1,4-cyclohexyl ring units to improve processability. Simple cross-polarization magic-angle-spinning (CPMAS) experiments compared the chlorine tolerance of BPS-20_PEG and PA. Techniques capable of detecting motional geometries and rates on timescales from nanoseconds to seconds, including relaxation time measurements, were applied. Correlations were established between relaxation time and water permeability for the RO membranes, and between relaxation time and polydispersity in the 1,4- cyclohexyl ring modified polymer. Next, 31P and 2H static ssNMR experiments evidencing the formation of toroidal pores and thinned bilayers in oriented zwitterionic and anionic phospholipid bilayers, (biomembrane mimetic systems), by the antimicrobial peptides (AMPs) magainin-2 and aurein-3.3, will be mentioned. The toroidal pore geometries induced by magainin-2 were different than those produced by aurien-3.3. The most prominent features were observed in 2H spectra, implying greater interaction of the peptides with hydrophobic lipid acyl chains. Following this, a new two-dimensional homonuclear dipolar recoupling MAS experiment, capable of correlating long range 13C-13C spin pairs in a uniformly/ extensively 13C-labeled biomolecule, will be introduced. This technique was demonstrated on 13C-labeled versions of Glutamine and Glycine-Alanine-Leucine. Experiments involving the recoupling of all 13C-13C spin pairs, and experiments with selective recoupling using Gaussian or cosine-modulated Gaussian pulses, were demonstrated. Finally, work using static 1H- 13C CP ssNMR to selectively detect interfacial water around hydrophobic C60 will be recounted. This project exploited the distance limitation of CP, and 1H spin-lattice relaxation times, to separate the influence of bulk and interfacial water on the spectra. Results indicated that the tumbling of interfacial water is slowed by a factor of 105 compared to bulk water, providing it with a solid-like character, and allowing the hydration shell to be stable at temperatures above the freezing point of water. / Ph. D.

No / Molecular mobility and physical form of co-spray-dried sugar:lysozyme formulations were evaluated. Co-spray-dried trehalose:lysozyme and sucrose:lysozyme formulations in 1:9, 1:1 and 9:1 ratios (w:w) were stored at 0% RH and 75% RH for 5-6 days. Molecular mobility and physical form of the co-spray-dried formulations after storage were determined by using 13C and 1H solid-state NMR as well as X-ray powder diffractometry. The results showed that increasing sugar content in co-spray-dried formulations stored at 0% RH decreased molecular mobility of the amorphous formulations indicating a close association of the protein and sugar. Exposure of sugar:lysozyme 1:1 and 9:1 formulations to 75% RH led to separation of sugar and protein phases, where the sugar phase was crystalline. The intimate sugar:lysozyme interaction of the formulations stored at 0% RH and the phase separation of the sugar-rich formulations stored at 75% RH were also confirmed by using 13C solid-state NMR spin-lattice relaxation time-filter (T1-filter) measurements. The propensity of sucrose and trehalose to crystallise was similar; however, the results suggest that part of the sugar in the phase-separated formulations remained amorphous and in close association with lysozyme.

Yes / In a competitive coformer exchange reaction, a recent topic of interest in pharmaceutical research, the coformer in a pharmaceutical cocrystal is exchanged with another coformer which is expected to form a cocrystal that is more stable. There will be a competition between coformers to form the most stable product through formation of hydrogen bonds. Thus, to monitor each and every step of such reactions, employing a very sensitive technique is crucial. 1H nuclear magnetic resonance (NMR) is a very powerful technique that is very sensitive to the hydrogen bond interactions. In this study, an in situ monitoring of a coformer exchange reaction is carried out by 1H magic angle spinning (MAS) solid-state NMR (SSNMR) at a spinning frequency of 60 KHz. The changes in caffeine maleic acid cocrystals on addition of glutaric acid, and caffeine glutaric cocrystal on addition of maleic acid were monitored. In all the reactions, it has been observed that caffeine glutaric acid Form I is formed. When glutaric acid was added to 2:1 caffeine maleic acid, the formation of metastable 1:1 caffeine glutaric acid Form I was observed, at the start of the experiment, indicating that the centrifugal pressure is enough for the formation. The difference in the end product of the reactions with similar reaction pathway of 1:1 and 2:1 reactant stoichiometry indicate that a complete replacement of maleic acid has only occurred only in the 1:1 stoichiometry of the reactants. The polymorphic transition of caffeine glutaric acid Form II to Form I at higher temperature was crucial reason which triggers the exchange of glutaric acid with maleic acid in the reaction of caffeine glutaric acid and maleic acid. Based on these results, new reaction pathways in competitive coformer exchange reactions could be distinguished, and the remarkable role of stoichiometry, polymorphism, temperature and centrifugal pressure could be established. / C.H. acknowledges Department of Science and Technology, India (DST), for the grant of Inspire Fellowship. T.G.A. acknowledges Council of Scientific and Industrial Research, India (CSIR) for research grants under the 12th 5 year plan project (Grant No. CSC0405). / The full-text of this article will be released for public view at the end of the publisher embargo on 19 Feb 2025.

NMR spectroscopy is a very powerful technique for the characterization of structure and dynamics of a variety of systems starting from small organic molecules to large biological macromolecules. In solids, the study of protons becomes more interesting because they are very sensitive to inter-molecular packing and are directly involved in hydrogen-bonding and aromatic π-π interactions, etc. The present thesis is devoted essentially to utilizing information from proton resonances obtained using multinuclear and multiple-quantum approaches. The thesis has two parts. The first part deals with methodological developments in the area of solid-state NMR, relevant to the study of rigid powder samples as well as partially ordered liquid crystalline materials. Methods have been proposed to investigate the structure of small molecules at moderate spinning frequencies and thermotropic liquid crystals at static conditions. Proton detected heteronuclear experimental methods based on both first and second-order cross polarization at moderate and ultra-fast magic angle spinning rates are also proposed. The second part of the thesis deals with the application of both newly proposed and existing solid state NMR methods to the study of several biologically relevant systems. These include the study of several designed as well as naturally occurring peptides. The use of first-principles calculations based on GIPAW method for supporting the experimentally obtained results has also been made. The thesis is divided into five chapters. In the second chapter, a new pulse sequence to correlate Double Quantum (DQ) proton frequencies to carbon Single Quantum (SQ) chemical shifts in the solid state has been proposed. In this sequence, named as MAS-J-1H (DQ)-13C-HMQC, the correlation between 1H and 13C is achieved through scalar coupling, while the double-quantum coherence among protons is generated through dipolar couplings. This experiment is particularly suited for the study of 13C in natural abundance. The advantages of the technique with applications to alanine, histidine and a model liquid crystalline material have been demonstrated. The assignment of 13C spectra of partially ordered systems has also been considered. In this case the assignment of the spectrum is a major challenge due to the interplay of anisotropic order and chemical shift parameters. The DQ-SQ correlation experiment described in the thesis has been applied to a well known liquid crystal and also to a novel thiophene based liquid crystal and the local order parameters of the liquid-crystal have been obtained. The thesis also presents results on the azelaic acid -isonicotinamide co-crystal as well as the drug ibuprofen obtained by using novel methodologies. In the case of the former, the problem of overlap of resonances was overcome with the use of the REVERSE-CP approach to separate out the carbon attached protons from the rest of the protons. Subsequently, by the use of several combined approaches, the structural features were identified. A new heteronuclear correlation pulse sequence for solids under fast MAS conditions has also been tested. With low r.f powers, a second-order dipolar term mediated transfer of magnetization between I and S spin known as second order cross-polarization (SOCP) was exploited to obtain the entire spin system connectivity. Both carbon detected and proton detected experiments have been carried out and their utility evaluated. Similar approaches to shed light on the structure and conformation of a set of proline and pseudoproline based designed β-turn peptides that are used as templates for understanding protein folding have been made. Results of studies on two biologically important forms of the short-chain peptides namely glutathione reduced (GSH) and oxidized (GSSG) tripeptides are also presented.

Nuclear Magnetic Resonance (NMR) and computational methods increasingly play a predominant and indispensable role in modern chemical research. The insights into the local nuclear environment that NMR can provide is unique information which allows the structural characterization of novel materials, as well as the understanding and explanation of their relevant properties on an atomic scale. Computational methods, on the other hand, can be used to support experimental findings, providing a rigorous theoretical basis. Furthermore, when more complex chemical systems are considered, calculations can prove to be invaluable for the interpretation of experimental data and often allow an otherwise impossible spectral assignment. This thesis presents a series of studies in which NMR spectroscopy, in combination with computational methods, is utilized to investigate a variety of chemical systems both in solution and the solid state. An overview of the thesis and experimental and computational details are given in Chapter 1. In Chapter 2, the quantum mechanical basis necessary for the description of the NMR phenomenon is presented. Chapter 3 explores the main experimental techniques employed routinely for the acquisition of NMR spectra in both solution and the solid state. Chapter 4 describes the main features of density functional theory (DFT) and its implementation in computational methods for the calculation of relevant NMR parameters. Chapter 5 reports an experimental solution-phase NMR study and a parallel computational investigation of the poly(CTFE-co-EVE) fluoropolymer. In Chapter 6, the combination of [superscript(14/15)]N solution-phase NMR techniques and DFT methods for the study of alkylammonium cationic templates used in the synthesis of microporous materials is presented. The characterization of a boroxoaromatic compound in the solid state and the study of its reactivity are described in Chapter 7. In Chapter 8, two experimental NMR methods for the study of the anisotropic chemical shift interaction in the solid state are compared and used to characterize a range of materials. Cross-polarization and nutation of quadrupolar nuclei are computationally investigated under both static and spinning conditions in Chapter 9. A general conclusion and a summary are given in Chapter 10.

The use of solid-state NMR and DFT calculations to study Y₂Sn[subscript(x)]Ti[subscript(2-x)]O₇, Y₂Sn[subscript(x)]Zr[subscript(2-x)]O₇ and Y₂Ti[subscript(x)]Zr[subscript(2-x)]O₇, materials with applications for the safe encapsulation of radioactive actinides is investigated. As a result of cation or anion disorder in these materials, NMR spectra are often complex and difficult to interpret. Therefore, an investigation using a range of NMR active nuclei and measurement of a variety of NMR parameters (isotropic chemical shift, δ[subscript(iso)]; span, Ω and quadrupolar coupling, C[subscript(Q)]) were used to provide a full and detailed picture of each material. The measurement of Ω in these disordered compounds with multiple resonances in the NMR spectra, required the use of 2D CSA-amplified PASS (CAPASS) experiments to enable the separation of each of the spinning sideband manifolds. An experimental assessment of the CAPASS experiment showed that although low ν₁/Ω[subscript(Hz)] ratios (as found in ⁸⁹Y NMR) resulted in distortions in the spectra obtained, a modified fitting procedure could be utilised to compensate for this fact, which allowed the accurate measurement of Ω. Despite the difficulties in acquiring the ⁸⁹Y NMR spectra, they were found to be the most informative of the NMR-active nuclei available. ¹¹⁹Sn NMR spectra, although much easier to acquire than ⁸⁹Y, were more complex and harder to analyse, owing to the overlapping resonances. Therefore, ¹¹⁹Sn NMR could only be used to confirm or support the results obtained using ⁸⁹Y NMR. Although ¹⁷O NMR was found to be useful, a full study could not be implemented due to the lack of ¹⁷O enriched samples; an area where future investigation may prove fruitful. Finally, [superscript(47/49)]Ti and ⁹¹Zr NMR spectra were found to be the most difficult to acquire due to their low receptivities and the quadrupolar broadened lineshapes, and as a result, little additional information was obtained. As a result of this analysis, for the Y₂Sn[subscript(x)]Ti[subscript(2-x)]O₇ pyrochlore solid solution, using primarily ⁸⁹Y δ[subscript(iso)] and Ω, and additionally confirmed with ¹¹⁹Sn δ[subscript(iso)], it was found that the Sn and Ti cations were randomly ordered throughout the B-sites. Additionally, ⁸⁹Y Ω could be used to obtain approximate Y-O[subscript(48f)] and Y-O[subscript(8b)] bond lengths for each type of Y environment. The study of Y₂Sn[subscript(x)]Zr[subscript(2-x)]O₇ using ⁸⁹Y NMR showed that although the end members were single phase, pyrochlore (Y₂Sn₂O₇) or defect fluorite (Y₂Zr₂O₇), the intermediate compositions were mostly two phase mixtures, consisting of an ordered pyrochlore (with an average formula of Y₂Sn₁.₈Zr₀.₂O₇) and a disordered phase, where the proportions of the pyrochlore and disordered phases decreased and increased, respectively, with the Zr content. Additionally, although the coordination states of the Y and Sn cations were easily determined using ⁸⁹Y and ¹¹⁹Sn NMR, respectively, the coordination states of the Zr cations could not be confirmed directly by ⁹¹Zr NMR. However, using indirect analysis from results obtained with ⁸⁹Y and ¹¹⁹Sn NMR, it was determined that 6 coordinate Zr was present in each composition, and it was always present in a greater proportion than 8 coordinate Zr. Finally, although ⁸⁹Y NMR spectra of Y₂Ti[subscript(x)]Zr[subscript(2-x)]O₇ were extremely difficult to analyse, it was tentatively proposed that they could be similar to Y₂Sn[subscript(x)]Zr[subscript(2-x)]O₇ due to some similarities observed between the spectra.

This thesis combines solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), chemical synthesis, isotopic enrichment and density-functional theory (DFT) calculations to provide insight into a number of microporous materials. The first class of materials studied is metal-organic frameworks (MOFs), where the presence of paramagnetic ions has a range of effects on the ¹³C NMR spectra, depending on the nature of the ligand-metal interactions. For the Cu²⁺-based MOFs, HKUST-1 and STAM-1, the assignment of the NMR spectra is non-intuitive, and unambiguous assignment requires specific ¹³C labelling of the organic linker species. It is shown that ¹³C NMR spectra of these two MOFs could act as a sensitive probe of the nature of “guest” molecules bound to the Cu²⁺. The second class of materials is aluminophosphates (AlPOs). It is shown that, using a series of relatively simple linear relationships with the crystal structure, the NMR parameters calculated by DFT (with calculation times of several hours) can be predicted, often with experimentally-useful accuracy, in a matter of seconds using the DIStortion analysis COde (DISCO), which is introduced here. The ambient hydration of the AlPO, JDF-2, to AlPO-53(A) is shown to occur slowly, with incomplete hydration after ~3 months. The resulting AlPO-53(A) is disordered and some possible models for this disorder are investigated by DFT. The final class of materials is gallophosphates (GaPOs), particularly GaPO-34 and related materials. The two as-prepared forms of GaPO-34 are characterised by solid-state NMR, and their calcination investigated by TGA and in-situ powder XRD. An unusual dehydrofluorinated intermediate phase is isolated and characterised for the first time by solid-state NMR. The fully calcined material is shown to be stable under anhydrous conditions, but hydrates rapidly in air. The hydrated material is stable under ambient conditions, but collapses upon heating. Partial dehydration without collapse is achieved by gentle heating or room-temperature evacuation. The impurity phases, GaPO₄ berlinite and GaPO-X are investigated by solid-state NMR and, while the structure of GaPO-X remains unknown, much structural information is obtained.