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By taking advantage of the unequal activity of the two NCO groups of toluene-2,4-diisocyanate at room temperature, a pure zirconium coordination compound with two reactive NCO functionalities is obtained, which can function as a precursor for polymerizations with organic primary amines and primary alcohols. A copolymer with poly(tetrahydrofuran) has been formed in this manner. A copolymer of Zr(sal)$\sb4$ (sal$\sp-$ = salicylaldehydato) and 3,3$\sp\prime$-diaminobenzidine, (Zr(tsdb)) $\sb{\rm n},$ which theoretically has one Zr(sal)$\sb2$ end-group and one diamine end-group in an average polymer chain, can strongly adhere to silica and alumina surfaces. To understand the hydrolytic behavior of the Zr(sal)$\sb2$ end-groups in the (Zr(tsdb)) $\sb{\rm n}$ polymer, the hydrolysis of Zr(sal)$\sb4$ has been studied by electronic, vibrational, and proton magnetic resonance spectroscopies. The results show that Zr(sal)$\sb4$ is almost insensitive to moisture in the solid state, but can be hydrolyzed quickly in solution. The adhesion of the (Zr(tsdb)) $\sb{\rm n}$ oligomer on silica or alumina has been further studied by x-ray photoelectron spectroscopy (XPS), including the use of Zr(sal)$\sb4$ as a model modifier. The XPS data show that both Zr(sal)$\sb4$ and (Zr(tsdb)) $\sb{\rm n}$ can strongly adhere to silica and/or alumina surfaces, and the adhesion of (Zr(tsdb)) $\sb{\rm n}$ is probably via both the Zr(sal)$\sb2$ and the diamine end-groups by forming the Zr-O-Si(Al) linkages and the (-NH$\sb2)($SiOH) H-bonds, and the latter may be broken under ultrasonication. Moreover, because (Zr(tsdb)) $\sb{\rm n}$ can initiate the polymerization of $\beta$-($\pm)$-butyrolactone ($\beta$-BL), a detailed study of the (Zr(tsdb)) $\sb{\rm n}$ initiated polymerization of $\beta$-BL has been conducted to clarify the polymerization mechanism. In addition, the polymerization of $\varepsilon$-caprolactone ($\varepsilon$-CL) has been also studied in the presence of (Zr(tsdb)) $\sb{\rm n}$. Model initiators, Zr(sal)$\sb4$ and o-diaminobenzene were used as well for comparison. The results from spectral and chromatographic investigations enable us to propose a dual-site ring-fission mechanism for the (Zr(tsdb)) $\sb{\rm n}$-initiated $\beta$-BL polymerization and a coordination-insertion mechanism for the Zr(sal)$\sb4$-initiated $\varepsilon$-CL polymerization.

Thermally induced phase separation in PS/PVME blends was studied by solid state NMR. The proton spin-lattice relaxation in both laboratory and the rotating frame were measured for the entire range of blend composition. Under conditions in which the blends are said to be compatible by other techniques, T$\sb{1\rho}\sp{\rm H}$ results obtained at -5$\sp\circ$C showed the fluctuation of local composition at a ten-angstrom scale. T$\sb{1\rho}\sp{\rm H}$ values at room temperature are closer to the longer relaxation time of PS than expected from simple weighted average of the relaxation times of the constituent homopolymers. This indicates incomplete averaging by spin diffusion and a restraining effect of PS on segmental motions of PVME. The blends were heated to cause phase separation and quenched. From the biphasic decay of $\sp{13}$C magnetization, the compositions of the separated phases were estimated to give a lower critical solution temperature phase diagram. NMR relaxation in PVME blends with PS molecular weight of 9K, 100K and 900K were compared. The mobility of the mesogenic group and the spacer in a series of twin liquid crystal polymers has been investigated by studying the cross polarization constant and the line width of $\sp{13}$C spectrum. Both moieties are found immobile in the crystalline state. The mesogenic group retains its rigidity while the spacer becomes mobile in the mesophase. The mobility of both moieties increases dramatically in the isotropic state. The mobility of the Si nuclei in a series of silarylene-siloxane copolymers has been investigated by studying $\sp{29}$Si NMR relaxation time. There is a correlation between the backbone mobility and the glass transition temperature. The lower the Tg, the more mobile is the molecule. The relaxation profiles for two of the samples can be superimposed by normalizing the free volume effect. The relaxation is dominated by the dipole-dipole interaction between Si and H.

The reaction of TiCl$\sb3$(THF)$\sb3$ with one equivalent of isopropyltetramethylcyclopentadienyllithium (7) in THF followed by oxidation with HCl afforded ($\eta\sp5$-(CH$\sb3$)$\sb2$CHC$\sb5$(CH$\sb3$)$\sb4$) TiCl$\sb3$ (8) in 66% yield. Treatment of 8 with C$\sb5$H$\sb5$Tl in refluxing benzene gave ($\eta\sp5$-(CH$\sb{\rm 3}$)$\sb2$CHC$\sb5$(CH$\sb3$)$\sb4$) ($\eta\sp5$-C$\sb5$H$\sb5$)TiCl$\sb2$ (9) in 95% yield. Reaction of TiCl$\sb3$(THF)$\sb3$ with two equivalents of 7 in THF followed by oxidation with HCl afforded ($\eta\sp5$-(CH$\sb3$)$\sb2$CHC$\sb5$(CH$\sb3$)$\sb4$) $\sb2$TiCl$\sb2$ (10) in 73% yield. Compound 10 was characterized by a single-crystal X-ray diffraction study. Ethylene polymerizations by 9/MAO (MAO = methylalumoxane), 10/MAO and Cp$\sb2$TiCl$\sb2$/MAO are compared at 1.3 atm. over the temperature range of 0-50$\sp\circ$C. Ethylene polymerizations by Cp$\sb2$ZrCl$\sb2$/MAO and Cp$\sb2$HfCl$\sb2$/MAO catalysts were compared. The Hf catalysts have about two-thirds the activity of the Zr catalysts. This difference may be attributed to the greater number of active centers present in the Zr catalyst. The Hf catalyst shows a smaller dependence of: (1) polymer molecular 45 reacts with CpTl to produce ($\eta\sp5$-1-vinyl-2,3,4,5-tetramethylcyclopentadienyl)($\eta \sp5$-cyclopentadienyl)titanium dichloride (46) in high yield. Reduction of CpTiCl$\sb3$ in THF by magnesium in the presence of ether excess trimethylphosphine or 2,6-dimethylphenylisonitrile at ca. $-$30$\sp\circ$C produces the titanium (III) complexes CpTiCl$\sb2$(PMe$\sb3$)$\sb2$ (51) and CpTiCl$\sb2$(CNC$\sb6$H$\sb3$(CH$\sb3$)$\sb2$) $\sb2$ (52), respectively, in good yields. The X-ray structure of 51 is reported. Reduction of Cp*TiCl$\sb3$ in THF by magnesium produces Cp*$\sb2$TiCl$\sb2$MgCl$\sb2$TiClCp* (53). A reaction of pentabenzylcyclopentadienyllithium with TiCl$\sb3$(THF)$\sb3$, followed by treatment with HCl gas produces ($\eta\sp5$-C$\sb5$Bz$\sb5$)TiCl$\sb3$ (54). An isomer of pentabenzylcyclopentadiene was characterized by 2d $\sp1$H $\times$ $\sp1$H NMR and $\sp{13}$C NMR methods and spectra were fully assigned.

New soluble linear cobalt(III) and chromium(III) $\beta$-diketone polymers have been prepared and characterized. Attempts to prepare linear coordination polymers analogous to the synthetic organic counterparts have historically posed serious problems for chemists particularly as a result of their intractability. In this study, bis($\beta$-diketonates) of the metal were first prepared and then allowed to react with sulfur halides of the form SCl$\sb2$ or S$\sb2$Cl$\sb2$ to yield thio- or dithio-bridged polymers, with the bridging occurring through the 3-carbons of the 2,4-diones. The polymers were found to be extremely soluble, with moderate molecular weights of at least 15,000 (as determined by NMR end-group analysis and viscosity measurements). GPC results were less satisfactory; they indicated polystyrene was not good as a standard for these polymers. Characterization of the materials was accomplished by Fourier-transform infrared (FT-IR), $\sp1$H- and $\sp{13}$C-nuclear magnetic resonance (NMR), pyrolysis-gas chromatograph/mass spectroscopy (py-GC/MS) and ultraviolet-visible (UV-vis) spectroscopy. Micro-analyses, gel permeation chromatography (GPC), thermal gravimetric analysis (TGA) and viscosity measurements were also performed. The synthesized materials also showed different degrees of thermostability (to at least 250$\sp\circ$C) and volatility as shown by their thermograms. In general, the trifluoroacetyl acetonate polymers were found to yield the more volatile polymers, while the Co(III)-containing materials were generally less volatile than their Cr(III) counterparts. A secondary goal of the investigation was to establish the ability of these materials to undergo chain scission upon exposure to radiation, with the reduction in molecular weight based on GPC measurements. Upon irradiation, GPC results clearly showed degradation to lower molecular weight materials. This reduction in molecular weight is an essential characteristic and requirement for positive acting resists, a possible application for these compounds.

The structure, morphology, phase transition behavior, and factors which govern the formation of helical crystalline syndiotactic polystyrene (sPS) have been investigated. The primary technique employed is vibrational spectroscopy, proven useful to obtain chain conformation distribution and chain and segmental orientation of polymers. Other techniques, such as wide angle X-ray diffraction and thermal analysis are used to characterize the crystalline state. Highly crystalline helical (TTGG) sPS has been prepared by isothermal growth from dilute solution, minimizing the amorphous structure. The crystals are observed to consist of a complexed structure of sPS and solvent molecules. Low frequency Raman spectra for sPS and their solvent complexes are reported. Although intramolecular, the phenyl ring torsion about the backbone is observed to be highly sensitive to the solvent complexed crystalline state and therefore the intermolecular ring environment. This suggests that such a band may be useful for examining the polymer-solvent specific interaction spectroscopically and therefore the mechanism of formation of the helical crystalline phase in sPS. The morphology of as-grown highly crystalline sPS/ethylbenzene mats consists of ribbon-like structures, which are irreversibly disrupted upon the expulsion of solvent from the crystal lattice. Complete molecular reordering during the helix to trans phase transition cannot be accounted for by cooperative bond rotation, consistent with the irreversible nature of the transition, and further emphasizing the critical role of solvent in the formation of helical crystallites. Crystalline syndiotactic polystyrene/solvent complexes prepared from different solvents exhibit a variety of different structures, as indicated by wide angle X-ray diffraction and thermal analysis. Differences in chain packing associated with these structures are reflected in the band shape and intensity of the low frequency phenyl ring torsional vibration. In addition, polarized infrared spectra show that phenyl rings of solvent molecules pack parallel to the syndiotactic polystyrene phenyl rings in these crystalline syndiotactic polystyrene/solvent complexes. A normal vibrational analysis is performed for the helical (TGGT) form of sPS. The calculated frequencies agree well with the observed infrared and Raman spectra, including conformationally sensitive bands.

L’objet majeur de cette étude est de contrôler la taille de nanoparticules de matériaux à transition de spin (TS), et d’étudier l’influence d’une réduction de taille sur les propriétés de commutation thermique. Plusieurs voies ont été explorées : La première stratégie basée sur la synthèse d’oligomères puis l’assemblage en unités supérieures s’est révélée difficile due à un manque de réactivité. La deuxième approche a consisté à utiliser le confinement moléculaire au sein d’une nanogouttelette pour synthétiser des oligomères de coordination de quelques nanomètres, et mettre en place une véritable “ingénierie moléculaire” en microémulsion. La dernière partie de ce travail est consacrée à la synthèse de particules à TS d’une centaine de nanomètre en milieu micellaire inverse permettant la discussion de l’influence de la taille des particules sur le comportement coopératif. / The main aim of this following study is to control the size of spin crossover nanoparticles, and investigate the influence of size reduction on thermal switch properties. The research has been undertaken along several approaches : Firstly a strategy was developed to build higher dimensionality from synthesized oligomers which revealed difficulties relevant to reactivity. The second approach consisted of using the molecular containment in a nanodrop to synthesize nanometric coordination oligomers and establish a real “molecular engineering” in microemulsion. The last part of this work is devoted to the synthesis of particles with spin crossover property as big as 100 nm in reverse micellar medium allowing the discussion of the interplay of their size with respect to the cooperative behaviour.

Um novo método de dissolução e acilação de celulose no sistema LiCl/N,N-dimetilacetamida (DMAC) foi desenvolvido e aplicado com sucesso nas seguintes celuloses: microcristalina (I), sisal (II), algodão(III) e bagaço de cana de açúcar (IV). O novo método tem as seguintes vantagens: a) uso de sistema acilante simples (anidridos alifáticos sem catalisadores); b) produção direta de ésteres simples (acetatos, propionatos e butiratos) e mistos (acetato/butirato), com eficiente controle do grau de esterificação; c) menor demanda de tempo e reagentes; d) desprezível degradação da celulose; e) eficiente recuperação/reciclagem do solvente e dos demais reagentes. Estudos por microscopia eletrônica de varredura revelam que em II e IV a penetração do solvente é mais lenta que em I devido à diferenças morfológicas. Constantes de velocidade e parâmetros de ativação do processo de descristalização de I e IV, foram determinados sob condições não isotérmicas, a partir do decaimento do índice de cristalinidade (determinado por espectroscopia no infravermelho). O processo de descristalização é globalmente endotérmico e aparentemente não depende do grau de polimerização (GP) da celulose de partida. A diferença na reatividade observada para as celuloses II a IV em relação a I, foi atribuída ao maior GP, maior flexibilidade da cadeia polimérica, além da agregação destas celuloses no sistema. O grau de acetilação individual das posições C6, C3 e C2 na unidade anidra de glicose, determinado por RMN de 13C, revela a seguinte ordem de reatividade para os grupos OH na UAG: C6 > C3 ≈ C2. / A novel procedure for cellulose dissolution and acylation in LiCl/ N,N-dimethylacetamide solvent system has been introduced and successfully applied to the following celluloses: microcrystalline (I), sisal (II), cotton (III) and sugar cane bagasse (IV). The novel procedure has the following attractive features: a) uses acid anhydride and requires no base catalyst; b) can be used for the direct preparation of esters and mixed esters; c) requires less amount of solvent and shorter time; d) causes negligible degradation of cellulose; e) permits recovery/recycling of DMAC and acid anhydride. Scanning electron microscopy studies show that swelling of celluloses II and IV by the solvent is slower than that of I, most probably due to morphological differences. Rate constants and activation parameters for decrystallization of I and IV have been determined from dependence of the index of crystallinity of cellulose, on time, under non-isothermal conditions. The decrystallization was found to be an endothermic process, negligibly dependent on the degree of polymerization (DP) of the starting cellulose. Differences in the reactivities between celluloses are related to GP, polymer chain flexibility and cellulose aggregation. The distribution of the acetyl moiety among the three OH groups was determined by 13C NMR, giving rise to the following order : C6 > C3 and C2.

Um novo método de dissolução e acilação de celulose no sistema LiCl/N,N-dimetilacetamida (DMAC) foi desenvolvido e aplicado com sucesso nas seguintes celuloses: microcristalina (I), sisal (II), algodão(III) e bagaço de cana de açúcar (IV). O novo método tem as seguintes vantagens: a) uso de sistema acilante simples (anidridos alifáticos sem catalisadores); b) produção direta de ésteres simples (acetatos, propionatos e butiratos) e mistos (acetato/butirato), com eficiente controle do grau de esterificação; c) menor demanda de tempo e reagentes; d) desprezível degradação da celulose; e) eficiente recuperação/reciclagem do solvente e dos demais reagentes. Estudos por microscopia eletrônica de varredura revelam que em II e IV a penetração do solvente é mais lenta que em I devido à diferenças morfológicas. Constantes de velocidade e parâmetros de ativação do processo de descristalização de I e IV, foram determinados sob condições não isotérmicas, a partir do decaimento do índice de cristalinidade (determinado por espectroscopia no infravermelho). O processo de descristalização é globalmente endotérmico e aparentemente não depende do grau de polimerização (GP) da celulose de partida. A diferença na reatividade observada para as celuloses II a IV em relação a I, foi atribuída ao maior GP, maior flexibilidade da cadeia polimérica, além da agregação destas celuloses no sistema. O grau de acetilação individual das posições C6, C3 e C2 na unidade anidra de glicose, determinado por RMN de 13C, revela a seguinte ordem de reatividade para os grupos OH na UAG: C6 > C3 ≈ C2. / A novel procedure for cellulose dissolution and acylation in LiCl/ N,N-dimethylacetamide solvent system has been introduced and successfully applied to the following celluloses: microcrystalline (I), sisal (II), cotton (III) and sugar cane bagasse (IV). The novel procedure has the following attractive features: a) uses acid anhydride and requires no base catalyst; b) can be used for the direct preparation of esters and mixed esters; c) requires less amount of solvent and shorter time; d) causes negligible degradation of cellulose; e) permits recovery/recycling of DMAC and acid anhydride. Scanning electron microscopy studies show that swelling of celluloses II and IV by the solvent is slower than that of I, most probably due to morphological differences. Rate constants and activation parameters for decrystallization of I and IV have been determined from dependence of the index of crystallinity of cellulose, on time, under non-isothermal conditions. The decrystallization was found to be an endothermic process, negligibly dependent on the degree of polymerization (DP) of the starting cellulose. Differences in the reactivities between celluloses are related to GP, polymer chain flexibility and cellulose aggregation. The distribution of the acetyl moiety among the three OH groups was determined by 13C NMR, giving rise to the following order : C6 > C3 and C2.

No description available.