The phase behaviors and microstructures of various realistic and model mixtures of macro and micro molecules, such as polyolefin solutions and nanoparticle block copolymer composites, have been accurately predicted by the application of Statistical Associating Fluid Theory (SAFT) based approaches through various extensions that improve both the physical description of molecular interactions and efficiency of computations. The extensions are presented in a generic sense that is applicable to other studies. These rigorously derived theories have been demonstrated to capture material structure-property relationships and can be applied broadly to other fields including biology, medicine and energy industry. On the phenomenogical scale, the novel SAFT-Dimer equation of state has been extended to study the liquid-liquid phase boundary (cloud point) in polyolefin solutions. A simplified model of the polyolefin molecules has been followed and the effect of various parameters, such as temperature, molecular weight, solvent quality and comonomer content, on the phase behavior has been successfully captured by the theoretical model through comparison with experimental measurements. The presented approach requires less parameters than previous methods and is of critical value to the industrial productions of polymers, especially polyolefins with long branches. On the molecular scale, the interfacial SAFT (iSAFT) Density Functional Theory (DFT) has been extended to include a dispersion free energy functional that explicitly accounts for molecular correlations. The Order-Disorder Transition (ODT) between lamellar and disordered phase has then been investigated for pure block copolymer and copolymer nanocomposite systems. The extension has been shown to dramatically improve the ODT predictions of iSAFT as well as the self assembled microstructures in nanocomposites over previous DFT calculations, in comparison to coarse grained molecular simulations. The behavior of the equilibrium spacing of ordered structures is also examined against the variation of copolymer size and interactions. An efficient numerical scheme, Fast Fourier Transform (FFT), has been implemented and shown to drastically increase the computation efficiency. The theory has then been extended to study block copolymer morphologies with density variations in multiple dimensions. Comprehensive phase diagrams including lamellar, cylindrical and disordered phases have been obtained for copolymer nanocomposites for the first time using a single framework molecular theory. In addition, the nanoparticle induced morphological transition between cylindrical and lamellar phase has been studied using a pseudo arc-length continuation method. Transition evolution is tracked and metastable morphologies are examined and compared with existing experimental reports and theoretical calculations. With these extensions, iSAFT offers a powerful prediction tool that closely relates molecular structure to thermophysical properties and provides an efficient alternative to screen parameter space for specified material properties.

Polyethylene terephthalate is one of the most important engineering thermal plastics used for fibers, films and bottles. Despite its wide applications and vast global market, PET has shortcomings, which limits it usage in many areas. PET has a glass transition temperature (Tg) of 80 DEGREE Celsius, this temperature is too low for certain applications. Increase in glass transition temperature, high temperature mechanical properties, and dimensional stability is of great importance to further expand the applications of PET. Significant research efforts have been made toward this goal, using a variety of approaches. In this work, we attempt to improve the properties of PET melt spun filament. Three strategies has been investigated (i) copolymerization of more rigid comonomer, 4, 4' bibenzoate unit into the PET structure, (ii) UV crosslinking of functionalized PET fiber, and (iii) Reinforcing PET matrix with carbon nanofibers.

A series of immiscible crystalline-crystalline diblock copolymers, poly(ethylene oxide)-b-(£`-caprolactone) (PEO-b-PCL), were blended with (3-phenyl-3,4-dihydro-2H-1,3-benzoxazin-6-yl) methanol (Pa-OH). FT-IR analyses provide that the ether group of PEO is a stronger hydrogen bond acceptor than the carbonyl group of PCL with the hydroxyl group of Pa-OH. Pa-OH after curing results in the excluded and confined PCL phase based on differential scanning calorimeter (DSC) analyses. In addition, the mesoporous structure was proved with the increasing the ratio of PCL to PEO in block copolymers by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) analyses and N2 adsorption-desorption isotherms (BET) The poly(styrene-b-4-vinyl pyridine) diblock copolymer was blended with Pa-OH monomer. FT-IR analyses demonstrate the intermolecular hydrogen bonding interaction between the pyridine group of P4VP and the hydroxyl group of Pa-OH. After curing, the block copolymers were incorporated into polybenzoxazine resin to access the nanostructure through the reaction induced microphase separation mechanism by TEM and SAXS analyses.

The fabrication of one-dimensional (1-D) polymeric photonic crystals from the self-assembly of ultra-high-Mw polystyrene-b-polyisoprene (PS-PI) block copolymers (BCPs) were conducted in this study. Well-ordered microphase-separated lamellar structures can be observed in the ultra-high-Mw PS-PI BCPs in the bulk by transmission electron microscopy (TEM) and ultra-small angle X-ray scattering (USAXS). To fabricate large-area and well-oriented lamellar microstructures with parallel orientation to the substrate, substrate-induced microstructural orientation with the accompanying solvent annealing method (i.e., solvent-induced orientation) was carried out in the PS-PI film. By grazing-incidence ultra-small angle X-ray scattering (GIUSAXS), scanning probe microscope (SPM) and cross-sectional TEM morphological observation, identification of the microstructural orientation in the PS-PI film can be achieved. A disordered wormlike morphology is observed in the as-spun PS-PI thin film from toluene on the PS-grafting substrate and on neat glass or wafer. This is attributed to the fast solidification of the disordered microstructure due to fast evaporation rate of the toluene solvent. After solvent annealing by the PS-selective or PI-selective solvents such as divinylbenzene (DVB) (neutral but highly PS-selective), benzene (PS-selective) and cyclohexane (PI-selective), parallel lamellar microstructures can be obtained in the PS-PI films on the PS-grafting substrate. By contrast, the coexistence of parallel and perpendicular lamellar microstructures is obtained in the PS-PI film from toluene after solvent annealing by neutral toluene on the PS-grafting substrate or by PS-selective benzene on the neat glass or wafer. This indicates that the formation of the parallel lamellar microstructures is mainly determined by both solvent-induced and substrate-induced orientation. In contrast to the as-spun disordered morphology from toluene, well-ordered parallel lamellar microstructures with few defects was found in the as-spun PS-PI film from DVB on the PS-grafting substrate, whereas parallel lamellar microstructures with many defects was observed in the as-spun PS-PI film from DVB on the neat glass or wafer. This further demonstrates that the PS-grafting substrate indeed plays an important role on the fabrication of well-ordered parallel lamellar microstructures. Interestingly, once the initial morphology of the PS-PI BCP reaches a relative stable state (i.e., parallel lamellar microstructures versus disordered wormlike morphology), it is hardly to trigger the microstructural reorientation by the subsequent solvent annealing. We suggest that the stable initial morphology in the PS-PI film may create high energy barrier for microstructural reorientation. With the controllable microstructural orientation, a PS-PI thick film having large-area and well-oriented parallel lamellar microstructures can be successfully carried out. Therefore, 1-D polymeric photonic crystals from the self-assembly of the lamella-forming PS-PI BCPs can be achieved. The in-situ UV reflectance spectra show that the reflective band shifts from ultraviolet wavelength to visible wavelength was observed in the lamella-forming PS-PI thick film with elapse of time by solvent annealing. Notably, the band gap can be recovered to the initial state once the solvent is removed, indicating the reversible process. As the results, the solvatochromic BCP photonic crystals can be successfully carried out by the manipulation of the solvent swelling in the large-area and well-oriented lamella-forming PS-PI BCP film.

Double crystalline block copolymers (BCPs), syndiotactic poly(4-methyl-1-pentene)-b-poly(L-lactide) (sPMP-PLLA) and syndiotactic poly(4-methylstyrene)-b-poly(L-lactide) (sPMS-PLLA), were synthesized to examine crystallization effect on the self-assembled morphologies in the double crystalline BCPs. Because of the stainable chemical structures, morphological observation can be carried out in these double crystalline BCPs. Also, different microphase-separated structures including lamellae and hexagonally packed cylinders were explored to study the shape effect for double crystallization. Based on differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) results, both sPMP and PLLA blocks are able to crystallize in the sPMP-PLLA BCP (fsPMPv=0.52) at the crystallization temperature (Tc) from 80¢XC to 120¢XC. Notably, temperature-dependent phase transitions between the PLLA polymorphisms are obtained by WAXD. By using small-angle X-ray scattering (SAXS) and transmission electron microscope (TEM), the microphase-separated lamellar structures can be observed in the sPMP-PLLA BCP (fsPMPv=0.52). Also, the preservation of the lamellar morphology at all Tcs (80¢XC~120¢XC) indicates that the sPMP and PLLA crystallization can be strongly confined within the lamellar microstructures due to the strong segregation strength of the sPMP-PLLA (fsPMPv=0.52) BCP. This can be further demonstrated by the ambiguous birefringence under polarized light microscope (PLM). According to the time-resolved SAXS and WAXD profiles at 90oC and 110oC, the sPMP block crystallizes first and induces the enlargement of the BCP long period. Also, the leading sPMP crystallization gives rise to the robust lamellar microstructural template and result in strong confinement for the subsequent PLLA crystallization. In the sPMS-PLLA BCP (fsPMSv=0.58), the microphase-separated lamellar nanostructures can be found by SAXS and TEM. DSC analysis shows that PLLA block is able to crystallize as Tc=90¢XC~100¢XC; the sPMS block is able to crystallize as Tc ≥120oC. By self-nucleation processes, both sPMS and PLLA blocks are able to crystallize. Therefore, by the manipulation of the respective crystallization, two-stage crystallization and coincident crystallization, systematic studies in the semi-crystallization, double crystallization and coincident double crystallization with the accompanying environmental Tg effect and BCP segregation strength can be carried out in the lamella-forming sPMS-PLLA (fsPMSv=0.58) BCP. By SAXS and TEM, the microphase-separated lamellar microstructures can be preserved in the self-assembly of the sPMS-PLLA (fsPMSv=0.58) BCP whatever the PLLA crystallization occurs under hard confinement (Tc,PLLA<Tg,sPMS) or soft confinement(Tc,PLLA˃Tg,sPMS). For the sPMS crystallization under soft confinement, the lamellar microstructures can be preserved as Tc,sPMS ≤140oC, whereas the breakout morphology by the sPMS crystallization is found as Tc,sPMS ≥150oC. As a result, the final morphologies is strongly dependent on the BCP segregation strength in the lamella-forming sPMS-PLLA (fsPMSv=0.58) BCP. In sPMS-PLLA BCP (fsPMSv=0.7), hexagonally-packed PLLA cylinders in the sPMS matrix are obtained by SAXS and TEM. DSC analysis shows that the sPMS block is able to crystallize as Tc=130¢XC~180¢XC, whereas no PLLA crystallization can be found in the cylinder-forming sPMS-PLLA BCP (fsPMSv=0.7). This indicates that the 2-D cylindrical shape might give rise to the strong confined effect and result in non-crystallizable PLLA. According SAXS and TEM results, the intrinsic hexagonally-packed cylinders can be preserved after the sPMS crystallization at 130oC due to the strong BCP segregation strength. By contrast, the crystallization driving force may overwhelm the microphase separation so as to form breakout morphology in the sPMS-PLLA (fsPMSv=0.7) BCP as Tc≥150¢XC.

The behavior of a protein molecule at the solid-liquid interface is a worthy scientific problem for at least three reasons. The main driving force for studying this problem is a practical one, as many areas of bio-related technologies, such as medical implants, biosensing, and drug delivery, require the understanding of protein-surface interactions. In this dissertation, the nature of the precursive weakly adsorbed state of proteins during binding is reviewed. From this perspective, the adsorption and binding of proteins to a solid block copolymer thin film was achieved with regular spacing. Further efforts produced a monolayer of green fluorescent protein (GFP) covalently bound with regular spacing and orientation to a diblock copolymer thin film. This protein could be folded and refolded by changing solvent characteristics. We also explored the binding of DC-SIGN to mannose and mannotriose bearing lipid membranes. While no binding was observed, the usefulness of the lipid-based glycan microarray was proven using the well-studied CTB-GM1 binding motif. / text

In an effort to develop broadly applicable photoswitchable catalysts, we have reported a method for modulating N-heterocyclic carbene (NHC) donicity using light by incorporating a photochromic diarylethene (DAE) into the backbone of a NHC scaffold. UV irradiation of 4,5-dithienylimidazolone or an analogous NHC-Ir(CO)₂Cl complex effected a photocyclization between the two thiophene rings, which led to a change in the electron donating ability of the NHC scaffold. Subsequent exposure to visible light reversed the photocyclization reaction. The concept of photo-modulating NHC donicity in this manner enabled photoswitchable NHC organocatalysis. The catalytic activity of a DAE-annulated imidazolium pre-catalyst in transesterification and amidation reactions was successfully switched between the active and nearly inactive states ([kappa]vis/[kappa]UV = 100) upon alternate UV ([lambda]irr = 313 nm) or visible ([lambda]irr > 500 nm) irradiation. The photoswitchable NHC organocatalysis was later extended to facilitating ring-opening polymerizations of cyclic esters, the rates of which were controlled via external light stimuli. Additionally, a photochromic dithienylethene-annulated N-heterocyclic carbene (NHC)-Rh(I) complex was synthesized and enabled photoswitching of the catalytic activity in series of hydroboration reactions. All of the examples demonstrate extremely rare instances of photomodulating a catalyst's activity by tuning its electronic properties. Furthermore, by taking advantage of the versatility of NHCs in both organo- and organometallic catalysis, we have developed novel photoswitchable catalysts for a variety of applicable transformations. Nanoparticles that can be transported in subsurface reservoirs at high salinities and temperatures are expected to have a major impact on enhanced oil recovery and electromagnetic imaging. We have developed an approach that will facilitate nanopaticle transport through porous media at high salinity by adsorbing or grafting rationally designed co-polymers on platform nanoparticles. Notably, co-polymers of acrylic acid with either 2-acrylamido-2-methylpropanesulfonate or styrenesulfonate have been electrostatically adsorbed or covalently grafted onto iron oxide nanoclusters. The presence of sulfonate groups on the iron oxide surface enabled long-term colloidal stability of the particles in extremely concentrated brine (8% wt. NaCl + 2% wt. CaCl₂) at elevated temperatures (90 °C) and minimized their adsorption on model mineral surfaces. / text

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