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Thesis (M.Sc.D.)--Boston University School of Graduate Dentistry, 1973. Orthodontics. / Bibliography included.

"New high performance optical systems require highly durable, broadband window materials in larger sizes than are currently available. To meet this need, a low cost edge-bonding process was developed for producing large area sapphire windows from smaller, melt-grown blanks. The method uses a polycrystalline alumina interlayer to promote diffusion and single crystal conversion at the interface between two sapphire substrates and produce high strength bonds. The goal of the current research effort is to determine the optimal alumina composition for maximum bond strength. Polycrystalline alumina fillets containing various chemical additives were prepared by tape casting for use in bonding trials. Oriented sapphire blanks were edge bonded in a furnace with special fixtures to accurately align and apply a load to the components during heat treatment. This approach is consistent with and builds upon the methods used in the previous edge-bonding studies. Flexure strength of the bonded samples, as compared to monolithic sapphire, was used as the performance metric. Additional bonding runs were carried out using the highest performing fillet composition in order to provide a sufficient number of specimens to conduct a Weibull analysis of the failure probability of the bonded material as a function of applied stress. A high purity alumina composition containing 3 wt.% SiO2, 0.05 wt.% MgO, and 0.05 wt.% Ti, produced the highest strength bonds. This composition yielded an average fracture strength of 255 MPa (37 kpsi), a Weibull modulus of 8.2, and a characteristic strength of 269 MPa (39 kpsi). These results compare favorably to monolithic sapphire specimens which yielded an average fracture strength of 284 MPa (41 kpsi)."

本論文描述了一系列由銅(I)催化-疊氮-端基炔環加成反應（CuAAC）而生成並具有分子内氫鍵的AABB型共聚主鏈（酰胺-三唑）化合物，並以此研究結構上的預組織對這一系列聚合物的聚合效率、物理性質和超分子性質的影響。 / 從衍生自吡啶-2,6-二甲酰胺或對苯二甲酰對苯二胺的二炔單體61或62與具有醌二疊氮化物單體63或64共聚，可獲得一系列重復單元内含兩個分子内氫鍵並具有不同内部結構的聚（酰胺-三唑）化合物。此外，一系列結構相似但重復單元内不含分子内氫鍵的二炔單體65-69也被用於與63或64共聚以作比較。透過核磁共振光譜法，質譜法，和/或尺寸排阻排阻色譜法（SEC）的鑑定能確認所有份子的結構。通過SEC分析結果顯示，只有每個重復單元内含分子内氫鍵的單體61或62得到的相應點擊聚合物才具有較高的DP值。這些結果表示，分子間的氫鍵能增強化合物結構的剛性從而減少環狀聚合物的產生，因而提高聚合度。 / 我們還發現，這些具預組織能猶的骨架的可以提升它們的自組裝能力，並促使它們在芳香溶劑裏形成可逆的有機凝膠。我們採用傅里葉轉換紅外光譜（FTIR）、X-射線粉末衍射（XRD）和掃描電子顯微鏡（SEM）對自組裝機制進行了研究。相比之下，重復單元内不含足夠分子内氫鍵的結構類似物65-69卻不能形成凝膠。 / 最後，我們發現，含有三唑基間苯二甲酰間苯二胺或三唑基吡啶-2,6-二甲酰胺基的聚（酰胺-三唑）化合物可以利用酰胺的NH和三唑的CH形成多個可結合滷素陰離子的位點。我們先用結構更簡單的寡聚類似物113-114和118模仿滷素陰離子(氯、溴、碘)結合強度，模式和機制。結果顯示，寡聚類似物與氯離子的結合強度明顯高於溴陰離子、碘陰離子是最弱的。有趣的是，間苯二甲酰間苯二胺的類似物對滷素陰離子的結合能力比吡啶-2,6-二甲酰胺類似物高得多。表明預組織的酰胺NH和三唑CH並沒有提供明顯對陰離子結合的優勢。相反，含有氮孤對的吡啶-2,6-二甲酰胺系統對滷素陰離子的結合的不穩定性影響更突出。根據此訊息，聚合物對滷素陰離子的結合特性就能得以估計。這研究結果得出一系列少數具有陰離子封裝能力的中性聚合物。 / This thesis described the copper(I)-catalyzed alkyne-azide AABB-type copolymerization of a series of main-chain poly(amide-triazole) compounds containing intramolecular hydrogen bond motifs, with the aim of understanding the effects of hydrogen bond-promoted preorganization on polymerization efficiencies and their physical and supramolecular properties. / A dialkyne monomer, 61 or 62 derived from pyridine-2,6-dicarboxamide or terephthalamide with two intramolecular hydrogen bonds per repeating unit, were synthesized and copolymerized with a diazide monomer, 63 or 64 respectively, to give the corresponding poly(amide-triazole)s (99 and 106) with different internal architecture. For comparison purposes, structurally similar dialkyne monomers 65-69 but with only one or no intramolecular hydrogen bonds per repeating unit were also prepared and copolymerized with the same diazide monomer 63 or 64 to give polymers 100-103 and 107. All compounds were characterized by a combination of nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and/or size exclusion chromatography (SEC). According to SEC analysis, it was found that monomers 61-62, with two intramolecular hydrogen bonds per repeating unit gave the corresponding click polymers with higher DP values. These results indicated that the imposed structural rigidity created by the intramolecular hydrogen bonds could reduce the amount of cyclic polymers and enhance the propagation growth of the polymerization process. / It was also discovered that such a preorganization along the backbone of poly(amide-triazole)s could enhance their self-assembly process and promote the formation of thermoreversible organogels in aromatic solvents. The assembly mechanisms were investigated by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The organogelating property was not observed in other structural analogues (100-103 and 107) that lack the sufficient number (i.e. 2 per repeating unit) of intramolecular hydrogen bonds. / Finally, it was found that poly(amide-triazole)s that contained repeating triazolyl isophthalamide or triazolyl pyridine-2,6-dicarboxamide motifs could utilize the amide NH and triazole CH groups to form multiple binding sites for halide anions. The halide (Cl⁻, Br⁻, I⁻) binding strengths, modes and mechanisms were first modeled using the structurally simpler oligomeric analogues 113-114 and 118. It was found that the binding strength of the chloride anion was higher than that of the bromide anion, and that of the iodide anion was the weakest. Interestingly, the isophthalamide analogues possessed a much higher binding ability towards anions than the pyridine-2,6-dicarboxamide analogues, suggesting preorganization of the amide NH and triazole CH groups did not offer substantial advantages towards anion binding. Rather, the destabilizing effect of the nitrogen lone pair on the pyridine-2,6-dicarboxamide system was more prominent. Based on this information, the binding properties of the polymeric analogues were then formulated. These results represent one of the few examples of a class of neutral polymers that possessed anion binding ability. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Yim, Sui Lung. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 150-156). / Abstracts also in Chinese.

Ethanol‐wet bonding (EW) has been proved to effectively infiltrate hydrophobic monomers into the demineralized hydrophilic dentin matrix and create a more degradation‐resistant network when bonding to normal dentin. Caries-affected dentin (CAD) has consistently demonstrated lower bond strength than normal dentin. Objective: To evaluate effect of EW on resin-CAD bond strength. Methods: Seventy five human molars with occlusal caries were randomly divided into water-wet (WW) and EW groups. CAD was obtained using the combined criteria of visual examination, surface hardness to an excavator and carbide bur and staining with 1% acid red in propylene glycol dye solution (Caries detector, Kuraray). For EW, the etched and water rinsed dentin was subsequently rinsed with absolute ethanol for 15s x3 before primer application. Four bonding agents, Bis-GMA/TEGDMA (ER2), Bis-GMA/HEMA (ER3), Bis-GMA/2-MP/HEMA (ER5), and Adper Scotchbond Multi Purpose (SBMP) were applied followed by resin-based composite (Heliomolar, Ivoclar Vivadent) incrementally built-up. Specimens (549) with a square cross-sectional area of approximately 0.7 mm2 were formed. Specimens (one day: 263; 6 month: 276) were subjected to micro-tensile bond test. Data were analyzed by one two-way and three-way ANOVA, two-sample t-test, and the parametric Weibull regression models. Result: There was a significant difference in the mean microtensile bond strength between WW and EW substrate condition for ER2 (p=0.0443). The mean microtensile bond strength with EW was significantly greater. Conclusion: Unlike prior research using normal dentin, EW bonding had significant effect only on 6 month bond strength to CAD for ER2.

OH-stretching spectra of various vapour phase species were recorded to investigate hydrogen bonding. The species studied include 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, acetylacetone, hexafluoroacetylacetone and the complex formed in the heterogeneous mixture of methanol and trimethylamine. The spectra range from the infrared, near infrared to visible wavelengths. The main focus of this study is in the near infrared region, in which the OH-stretching overtones are dominant. The near infrared and visible spectrum of formic acid has been recorded to investigate coupling across bonds, specifically a resonance occurring between OH- and CH-stretching vibrations. The same resonance was also observed in the spectrum of 1,2-ethanediol. The spectra of deuterated isotopomers of formic acid and 1,2-ethanediol were recorded to experimentally verify the resonance. The inherently weak nature of the vibrational overtone transitions required sensitive spectroscopic techniques to observe the spectra. The spectra were recorded with conventional long path length absorption spectroscopy and intracavity laser photoacoustic spectroscopy. Anharmonic oscillator local mode calculations of the OH-stretching transitions were performed to simulate the observed spectra. These calculations require calculation of potential energy surfaces and dipole moment functions. Simulated spectra obtained with highly correlated ab initio methods and large basis sets have yielded the best agreement with observation.