This thesis describes the use of bisphenol a carbonate cyclic oligomers (BPACY) as novel building blocks for polymer blends. The objective of the initial phase of this research is to determine whether the thermodynamics of mixing are affected by changes in the topology of a mixture's components. The second phase of this research involves the in-situ polymerization of BPACY in miscible thermoplastic matrices. The thermodynamics of mixing have been shown to be quite sensitive to changes in the topology of blend components. Cyclic bisphenol a carbonate cyclic oligomers are miscible with a wider range of polystyrene molecular weights than are chemically equivalent linear oligomers. The Flory-Huggins mean field theory predicts the shape of phase boundaries quite well for linear polystyrene (PS) /linear polycarbonate (PC) blends as well as for linear polystyrene/cyclic polycarbonate blends. However, the interaction parameter was determined to be strongly dependent upon topology with $\rm\chi\sb{PS\sb{L}/PC\sb{C}}<\chi\sb{PS\sb{L}/PC\sb{L}}.$ This result has been explained in terms of a topological interaction unique to ring polymers which is expected to be quite general. The in-situ polymerization of BPACY/styrene-acrylonitrile copolymer (SAN) blends has been demonstrated to yield PC/SAN blends with morphologies unattainable via conventional melt blending. Extremely fine phase dispersion can be obtained by this method of blend preparation. The domain coarsening kinetics have been shown to be quite sensitive to the volume fraction of the dispersed phase. The "pinning" of domain coarsening, unique to polymer systems, can be attributed to the extreme barriers to diffusive coarsening mechanisms in these systems. Thus, phase coarsening is arrested when percolation ceases or domains no longer form local clusters. The dispersed phase size has been shown to have a dramatic effect on high stress deformation in systems where a brittle phase is dispersed in a more compliant ductile matrix. The increased ductility of blends with finer phase dispersions has been rationalized based on a lower tendency for smaller brittle phases to craze/crack in addition to the influence of complex local stress fields in heterogeneous materials.

The techniques of neutron and x-ray scattering have been used to study the morphology and crystallization behavior of polyethylene and blends of polyethylene. Synchrotron radiation was used to study the crystallization behavior of blends of high density polyethylene/ low density polyethylene (HDPE/LDPE) and linear low density/ low density polyethylene (LLDPE/LDPE). Simultaneous real time small and wide angle scattering from blends slowly cooled at (0.5$\sp\circ$C/min) seem to indicate that the lamellae are formed in bundles of primarily one component. For blends quickly cooled from the melt (quenched to 60$\sp\circ$C) on the other hand, the lamellae are randomly mixed together. HDPE/LDPE and LLDPE/LDPE blends show qualitatively the same crystallization behavior throughout the composition range except for 10%/90% LLDPE/LDPE. At this composition, extensive cocrystallization may be occurring in even slowly cooled samples. Small angle neutron and x-ray scattering was used to determine the location of the short chain branches in selectively deuterated LLDPE. Specially prepared LLDPE with the main chain deuterated was used in these experiments to provide contrast for neutron scattering. Despite density contributions to the neutron scattering from crystalline and amorphous regions, differences between the x-ray and neutron scattering suggest that the concentration of branches may be enhanced at the crystal- amorphous boundary. The extent of this branch-rich region was estimated to be about 30A. Lastly, the chain orientation of ultra high molecular weight PE (UHMWPE) was examined by small angle neutron scattering. A circularly averaging technique was applied in order to avoid sample alignment problems. Between extension ratios of 12 and 60, hot drawn (125$\sp\circ$C) gel crystallized UHMWPE does not show appreciable change in the perpendicular radius of gyration. However, changes in the asymptotic behavior of the scattering intensity from I $\sim$ q$\sp{-1.56}$ at 12x to I $\sim$ q$\sp{-1.2}$ at 60x indicate a change in geometry toward more rod like segments in the higher drawn material.

The effect of crosslinking on the phase stability and phase separation behavior of poly(vinyl methyl ether)/polystyrene semi-IPN was studied by light scattering. The cloud point temperature was measured as a function of degree of crosslinking and found to be constant within experimental precision. The result of this experiment was combined with a theoretical prediction of the phase diagram to determine conditions for the following experiment. Wide angle light scattering was used to quantitatively analyze the mechanism and dynamics of the thermally induced phase separation with respect to the crosslinking density and the thermal condition. An apparatus with a one dimensional diode array was used to simultaneously monitor a wide range of scattering angles. Analysis of the early stages of phase separation indicates that the spinodal temperature remained virtually constant whether or not crosslinks were present in the system. This was demonstrated to be consistent with theoretical prediction. However, the apparent diffusion coefficient decreased dramatically with the introduction of crosslinks thus the initial phase separation was slowed down significantly. The final scattering intensity was shown to decrease with increasing crosslinking density. The scattering vector dependence of the scattering intensity was negligible compared with its overall time dependence. A plateau region was observed for some of the scattering intensity data of the semi-IPN systems with respect to time. This indicates that the crosslinks restrict terminal phase contrast and not the size of phase.

Investigations focused on the lower critical solution temperature (LCST) exhibited by poly(N-isopropylacrylamide) (PNIPAAM) in aqueous solution. The perturbation of this transition by the addition of cosolutes and by copolymerization was examined through the application of microcalorimetry, fluorescence spectroscopy, surface tensiometry, and cloud point measurements. Cosolutes employed included polar solvents, inorganic salts, amphiphiles, and other macromolecules. Copolymerization incorporated very small amounts (less than 2 mol %) of fluorescent derivatives or N-hexadecylacrylamide (HDAM). The microcalorimetric method was established through analyzing endotherms observed upon heating various samples of PNIPAAM and other polymers that exhibit LCSTs in aqueous solution; comparisons were made with classical cloud point curves. The properties of ternary solutions were then determined. Substituting miscible polar solvents for water lead to the phenomenon of cononsolvency. Transitions present in water-methanol mixtures were quantitatively related to those found by Hirotsu in crosslinked gels of PNIPAAM. The effects of low concentrations of poly(vinyl methyl ether) (PVME) and polyacrylamide were briefly studied. The influence of PNIPAAM on the association of amphiphiles characterized by a wide range of head group and tail structures was measured. Changes in critical surfactant concentrations and bilayer transition endotherms were correlated with reciprocal effects on the LCST of PNIPAAM to establish a hierarchy of complexation strengths. Use of free probes was complemented by applying fluorescent amphiphiles and polymer-bound fluorophores. This last approach was applied not only as an environmental micropolarity sensor but also in nonradiative energy transfer experiments. Solutions of PNIPAAM/HDAM copolymers were concluded to be micellar via the above methods. Solubilization sites of probes were estimated based upon their sensitivity to the LCST. Adding amphiphiles and varying polymer concentration also aided in establishing a microheterogeneous state.

The structure and permeability of phosphatidylcholine bilayer membranes prepared in the presence of azobenzene and spirobenzopyran modified poly(methacrylic acid) and poly(2-ethylacrylic acid) were studied as a function of the isomeric state of the bound chromophores. Poly(methacrylic acid) modified with 10.4 mole% azobenzene units (PMAZ) and poly(2-ethylacryIic acid) modified with 4 mole% azobenzene units (PEAZ) were prepared by free radical polymerization of the corresponding acrylic acid with N-4-(phenylazo)phenyl methacrylamide. Poly(methacrylic acid) modified with 1.5 mole% spirobenzopyran units (PMSP) and poly(2-ethyIacryIic acid) modified with 5.2 mole% spirobenzopyran (PESP) units were prepared by first incorporating pendant nitrosalicylaldehyde units into the polymer with subsequent conversion to the spirobenzopyran units. Each of these polymers undergoes a transition from a collapsed coil to an expanded chain and this transition is unaffected by the conformation of the pendant chromophore. The ability of these polymers to associate with phosphatidylcholine bilayer membranes is dependent upon the nature of the chromophore. With PMAZ and PEAZ a greater extent of polymer-lipid association was detected when the azobenzene was in the trans conformation as compared to the cis azobenzene conformation. For PMSP and PESP greater association was detected when the chromophore was in the spiropyran conformation as compared to the merocyanine form. Larger extents of association were observed as broadening of the vesicle phase transition. The change in polymer-lipid association is attributed to the difference in polarity of the two forms of the chromophores. The permeability of the membranes could be sensitized to light only in the presence of PEAZ and PESP. With PEAZ the permeability of the membranes could be reversibly photomodulated.

The structural reorganization of vesicle membranes that occur due to a pH dependent complexation of the membranes with poly(2-ethylacrylic acid) (PEAA) was investigated. The kinetics of the reorganization were examined by monitoring the changes in the turbidity of vesicle suspensions that occurs during the reorganization. The response of the rate of reorganization to pH, temperature, and membrane composition was studied. It was found that the reorganization behaved similarly to the solubilization of phosphatidylcholine vesicle by apolipoproteins. Permeability changes accompanying the process were recorded by monitoring the fluorescence changes of vesicle suspensions containing a fluorescent marker. The rate of change in permeability was found to be fast relative to the rate of structural reorganization. PEAA was labeled with the dansyl chromophore. Fluorescence microscopy was used to visualize the interaction of the labeled polymer (DnsPEAA) with egg yolk phosphatidylcholine vesicles. Adsorption of DnsPEAA onto vesicle surfaces produced a concentration of fluorescence on the vesicles. Following acidification of these samples, vesicles reorganized into many smaller particles with a diffusion of fluorescence. The reorganization was sensitized to the presence of glucose by incorporating the enzyme, glucose oxidase, into vesicles suspensions containing PEAA. The rate of permeability increase of membranes could be controlled by adjusting the concentrations glucose, enzyme, oxygen and PEAA.

The thermal reconstruction (80-110$\sp\circ$C) of surface-modified films of poly(chlorotrifluoroethylene) (PCTFE) was studied by contact angle and x-ray photoelectron spectroscopy. The modified surfaces studied, synthesized via the reaction of PCTFE with lithium reagents, were PCTFE-TMO (containing a 10 A thick modified layer of dimethyl-oxazoline functionality), PCTFE-COOH (produced by hydrolysis of PCTFE-TMO), PCTFE-OH (30 A and 1100 A thick modified layers), and PCTFE-OC(O)CH$\sb3$, PCTFE-OC(O)CF$\sb3$, PCTFE-OSiMe$\sb3$, and PCTFE-OC(O)(CF$\sb2$)$\sb3$CF$\sb3$ (produced by reaction of 30 A-modified PCTFE-OH). Two reorganization processes are evident--one occurs in PCTFE-TMO and PCTFE-OH (30 A) for which changes are observed both by contact angle and XPS; migration of PCTFE units into the outer 10 A is proposed. Another process is evident in the reconstruction of PCTFE-OC(O)CH$\sb3$ and PCTFE-OH (1150 A) for which only a contact angle change is observed; repeat units do not measureably migrate and rotation is proposed. The heterogeneous (gas-solid) reaction of polyethylene films with chlorine gas was studied with the goal of confining the chlorination to the surface (outer $\sim$100 A) of the film. The effect of chlorine concentration, light intensity, and reaction time on the depth of chlorination (thickness of the modified layer) and extent of chlorination (density of chlorine substitution on the PE chain) was studied by XPS, ATR-IR, TIR, and gravimetric analysis. Chlorination with 1 atm. Cl$\sb2$ in the dark gave a low extent of substitution ($\sim$1 Cl per 9 C after 22 h) although the reaction proceeded deeply into the film. Chlorination with 1 atm. Cl$\sb2$ under UV or visible light gave more highly chlorinated surfaces ($\sim$1 Cl per C in 2 min.) and the reaction occurred more surface-selectively. Chlorination with low chlorine pressures (2-50 mm) was used to prepare samples with very thin ($<$100 A thick) chlorinated layers. A variety of reactions of the chlorinated (and brominated) polyethylene surfaces were attempted in order to assess the feasibility of using the surface-confined alkyl halides as a reactive handle for the synthesis of other modified polyethylene surfaces. Although the halogenated surfaces could be partially dehydrohalogenated (and the resulting double bonds could be brominated or hydroborated and oxidized) substitution reactions were unsuccessful.

Biodegradable polymers, for biodegradable plastic utility and drug release biomedical applications, are the primary objectives of this thesis research. We have synthesized poly($\beta$-hydroxybutyrate) (PHB), poly($\beta$-malic acid) (PMA) and their copolymers by the ring-opening polymerization reactions of $\beta$-butyrolactone and $\beta$-benzyl malolactonate. A varity of catalysts were used, including the stereoregulating catalysts, ethyl aluminoxane (EAO) and the product of the in-situ preparation of Et$\sb3$Al/H$\sb2$O, as well as the non-stereoselective catalysts, Et$\sb2$Zn/H$\sb2$O and (5,10,15,20-tetraphenylporphinato)aluminum chloride (TPPAlCl). The degree of stereoregulation of the homopolymers was enhanced by the use of a stereoregulating catalyst, followed by product extraction. The resulting insoluble fractions of PHB and PBML are stereoregular crystalline polymers having high molecular weights, with the former compared with naturally occurring P( (R) -HB) in corresponding properties. The stereoregularity of the synthetic polymers was determined by $\sp{13}$C (75.4 MHz) NMR spectroscopy, differential scanning calorimetry (DSC) and FTIR spectroscopy. The yield of polymerization was optimized by using the Et$\sb2$Zn/H$\sb2$O and TPPAlCl catalysts, resulting the amorphous polymers with relatively low molecular weights. The analysis of copolymer tacticity and comonomer sequences by using $\sp{13}$C-NMR and DSC indicates a random distribution of the copolymer sequences. The stereochemical course of the ring-opening polymerization of BL with the Et$\sb3$Al/H$\sb2$O and Et$\sb2$Zn/H$\sb2$O catalysts was studied using (S) -BL as a stereochemical probe. The (S) -$\beta$-BL, which was prepared in five steps from naturally occurring P( (R) -HB), had an optical purity in excess of 97% as measured by $\sp1$H NMR spectroscopy in the presence of a chiral europium shift reagent, Eu(hfc)$\sb3$. The stereochemical configuration and isomeric purity of the repeating units in the polymers obtained were determined both from their specific optical rotation and by degradation of the polymers to their component methyl $\beta$-hydroxybutyrate units. From our investigations it was concluded that the ring-opening reaction can be carried out by different routes in the Al- and/or Zn-water catalysts, and the two enantiomers, P((R) -HB) and P((S) -HB) were obtained as the result of the configuration retention or inversion. These enantiomers of PHB are very useful for the study of the stereochemistry of synthetic poly($\beta$-lactone)s and their biodegradability.

Dynamic light scattering (DLS) and forced Rayleigh scattering (FRS) were used to study polymer diffusion in solution in two kinds of porous materials: porous glasses and suspensions and gels formed from fumed silica particles. The diffusants were: dendritic polyamidoamines, linear polystyrenes, and dye-labeled polystyrenes. Polymer diffusion in porous glasses was investigated, by using DLS, as a function of time scale (t), polymer hydrodynamic radius (R$\sb{\rm H}$), and pore radius (R$\sb{\rm P}$). As t increases, the apparent diffusion crosses over from single pore diffusion (in which steric obstruction is weak) to macroscopic diffusion (in which the tortuosity of the pore networks is fully effective). Computer simulated diffusion agreed qualitatively with the crossover observed by DLS. The dependence of hindered diffusion on the size ratio $\lambda\sb{\rm H}$ = R$\sb{\rm H}$/R$\sb{\rm P}$ was studied for dendritic polyamidoamines and linear polystyrenes in porous glasses. For $\lambda\sb{\rm H}$ $\ll$ 1, when hydrodynamic interactions dominate, dendritic polymers diffuse more slowly than linear polymers of comparable $\lambda\sb{\rm H}$. The diffusion results of the dendritic polymer and of the linear flexible polymer agreed quantitatively with the hydrodynamic theories for a hard sphere in a cylindrical pore, and for a random-coil macromolecule in a cylindrical pore, respectively. At large $\lambda\sb{\rm H}$, irregularities in local pore size lead to conformational entropy changes as the macromolecule moves. The experimental data agree qualitatively with the entropy barrier theory. Diffusion of dye-labeled polystyrenes within gels and suspensions formed from fumed silica was studied using FRS. Untreated silica was found to adsorb the labeled polymer, leading to strong hindrance even at very low silica concentration. Thorough quenching of the silica surface by silanization prevented polymer adsorption. The dependence on silica volume fraction of the resulting weakly hindered diffusion in treated silica was found to be consistent with simple theories of steric obstruction.

This thesis describes the synthesis and characterization of segmented and triblock copoplymers with mesogenic hard blocks and flexible spacer soft blocks. Three series of segmented block copolymers, one series of twin liquid crystal (LC) polymers and a variety of model compounds have been prepared. The first series of segmented block copolymers consist of potentially mesogenic dyad hard block and oligomeric flexible spacers. These materials are not liquid crystalline, although chain extended analogs do show elasticity and strength. The second and third series of segmented polymers consists of well defined tetrad and pentad mesogenic blocks. These polymers and their analogous model compounds exhibit liquid crystallinity. The preparation of these materials involved the condensation of a bisphenolic prepolymer of, either poly(tetramethylene ether)glycol, polyTHF, or polypropylene glycol, PPG, of varying molecular weight, with a variety of aromatic diacid chlorides: 4,4$\sp\prime$-azobiphenylene, 4,4$\sp\prime$-azoxybiphenylene, 4,4$\sp\prime$-biphenylene, 2,6-naphthalene and 4,4$\sp\prime$-terephthaloyloxybiphenylene. The resulting polymers are liquid crystalline and exhibit reproducible melt transitions by differential scanning calorimetry, DSC and polarized optical microscopy, POM. The polymer melts are birefringent, and textures for some of the polymers are consistent with either smectic or nematic mesophases. The LC polymers show a convergence of Ti with Tm as the spacer length increases from 40 to $\sim$200 atoms. It is also shown that the type of polymeric soft segment used to prepare tetrad LC polymers has a remarkable effect on the liquid crystallinity and physical properties of the resulting polymer. Finally, variations in the hard block can dramatically effect both the stability and structure of a liquid crystalline phase. In the final section, "twin" or triblock LC polymers are described. These polymers were prepared to compare thermal properties of segmented vs. triblock copolymers with chemically identical blocks. The preparation involved the synthesis of a novel mono functional mesogen. The twins exhibit thermal trends similar to those of the corresponding segmented polymers.