Tetramethyl bisphenol-A Polycarbonate Research Articles

The Elastic Mechanical Response of Nanoscale Thin Films of Miscible Polymer/Polymer Blends

Nanoindentation measurements of the elastic moduli Er of thin polymer films supported by stiff substrates with moduli Es ≫ Er show an increase of Er with decreasing h, for h less than a threshold thickness ht. In the thickness range h < ht , the value of the modulus manifests the influence of various interactions associated with the “stiff” substrate. We show that ht is a function of composition for the miscible blend of polystyrene (PS) and tetramethyl bisphenol-A polycarbonate (TMPC). The modulus Er,TMPC of TMPC films supported by SiOx increases for h < ht(TMPC) ∼ 300 nm while ht(PS) ∼ 450 nm for the modulus Er,PS of PS films, supported by the same substrate. The threshold thicknesses of the blends and the moduli of the blends appear to be reasonably described by an effective medium approximation. This behavior is rationalized in terms of the vibrational force constants f, determined using incoherent neutron scattering experiments, of the materials.

Characterization of the microvoids of a tetramethyl polycarbonate/polystyrene blend system using Xe sorption measurements and 129Xe NMR spectroscopy

Xe sorption properties of tetramethyl bisphenol A polycarbonate (TMPC)/polystyrene (PS) blends indicated the reduction of microvoids by blending. From the analysis of 129Xe NMR chemical shifts of the 129Xe in these blends, the mean volume of individual microvoids (v) was calculated. The v values for these blends were smaller than those of predicted by a simple additive rule, as well as the cases of variation of density and Xe sorption properties. This fact indicates that the volume contraction induced by blending for TMPC/PS blends is mainly attributed to contraction volume of individual microvoids.

Micellar Formation and Organization in Thin Film Polymer Blends

We study the formation and organization of micelles, of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer chains, in thin film hosts composed of (1) blends of long and short chain polystyrenes, PSL and PSS, of degrees of polymerization PL and PS, respectively (PS < PL), and (2) blends of PSL and a homopolymer with which it is compatible, tetramethyl bisphenol-A polycarbonate (TMPC), of degree of polymerization PTMPC (PTMPC < PL). The role of competing entropic and enthalpic interactions on the block copolymer micelle formation and organization is examined. We show that the average size of the micelle cores, Dcore, decreased with increasing weight fraction of the shorter chain PS component in PS(PS = 125)/PS(PL = 15400) mixtures, for PL≫NPS, NPS is the degree of polymerization of the PS block (the micelle corona). Dcore also decreased with increasing weight fraction of TMPC in TMPC(PTMPC = 122)/PS(PL = 15400) mixtures. The values of Dcore in the TMPC/PSL hosts were smaller than those in PSS/PSL mixtures, for the same TMPC, or PSS, weight fractions (PS ≈ PTMPC). This is due to more extensive mixing between the TMPC host chains, compared to the PSS chains, and the micelle corona. Furthermore, we show that the size and the organization of the micelles within the films may be controlled independently, through changing the relative fractions of PSS or TMPC and the value of PL. The fraction of TMPC, or PSS, mixed with the corona decreased as PL decreased from PL = 15400 to smaller values.

Structure of thin film polymer/nanoparticle systems: polystyrene (PS) coated-Au nanoparticle/tetramethyl bisphenol-A polycarbonate mixtures (TMPC)

The morphologies of thin film blends of polystyrene (PS)-brush coated Au nanoparticles with tetramethyl bisphenol-A polycarbonate (TMPC) were investigated. Our results reveal that entropic effects, associated with the brush/host chain interactions, nanoparticle diameter, D, and asymmetries in monomer sizes of the host and grafted chains, can play a more important role than the favorable PS/TMPC enthalpic interactions toward determining the phase miscibility of the system. A diagram of states is constructed to show the phase separated and dispersed regimes as a function of D, N, the degree of polymerization of the grafted chains, and P, the degree of polymerization of the host chains, at a constant grafting density. These results have important implications on the design of brush coated nanoparticle/homopolymer mixtures for various applications.

Dewetting dynamics in miscible polymer-polymer thin film mixtures

Thin polystyrene films supported by oxidized silicon (SiOx/Si) substrates may be unstable or metastable, depending on the film thickness, h, and can ultimately dewet the substrate when heated above their glass transition. In the metastable regime, holes nucleate throughout the film and subsequently grow due to capillary driving forces. Recent studies have shown that the addition of a second component, such as a copolymer or miscible polymer, can suppress the dewetting process and stabilize the film. We examined the hole growth dynamics and the hole morphology in thin film mixtures composed of polystyrene and tetramethyl bisphenol-A polycarbonate (TMPC) supported by SiOx/Si substrates. The hole growth velocity decreased with increasing TMPC content beyond that expected from changes in the bulk viscosity. The authors show that the suppression of the dewetting velocity is primarily due to reductions in the capillary driving force for dewetting and to increased friction at the substrate-polymer interface. The viscosity, as determined from the hole growth dynamics, decreases with decreasing film thickness, and is connected to a depression of the glass transition of the film.

Control of Interfacial Instabilities in Thin Polymer Films with the Addition of a Miscible Component

We show that while polystyrene (PS) thin films are structurally unstable on oxidized silicon wafers, the addition of as little as a few weight percent tetramethylbisphenol A polycarbonate (TMPC) has a stabilizing effect on the topographical structure of the films. The stabilization is evident from the existence of a threshold TMPC concentration, φt, and a threshold thickness, ht, beyond which films do not dewet. The concentration threshold occurs for φTMPC ≤ 0.10. An examination of the effective interface potential, which accounts for short- and long-range intermolecular interactions, indicates that this dewetting inhibition is metastable.

Dispersion of gold nanoclusters in TMBPA-polycarbonate by a combination of thermal embedding and vapour-induced crystallization

Gold nanoclusters can be dispersed into the surface of a bisphenol-A polycarbonate film by acetone vapour induced crystallization, an effect which has been demonstrated in a previous publication of our group. Gold nanoclusters were deposited by physical vapour deposition on an amorphous thin film of polycarbonate. After vapour induced crystallization these clusters were detected by depth profiling to be embedded into the surface, with a concentration maximum in a depth of approximately 100 nm. In this work, we replaced the BPA by the modified tetramethyl bisphenol-A polycarbonate, which shows a slower crystallization kinetics. A strong enhancement of the dispersion depth has been achieved by thermal pre-embedding of the clusters into the surface. Surface analysis by means of atomic force microscopy reflects the rearrangement of polymer material in the course of crystallization.

Glass Transition of Miscible Binary Polymer-Polymer Thin Films

The average glass transition temperatures, Tg, of thin homopolymer films exhibit a thickness dependence, Tg(h), associated with a confinement effect and with polymer-segment-interface interactions. The Tg's of completely miscible thin film blends of tetramethyl bisphenol-A polycarbonate (TMPC) and deuterated polystyrene (dPS), supported by SiO(x)/Si, decrease with decreasing h for PS weight fractions phi >0.1. This dependence is similar to that of PS and opposite to that of TMPC thin films. Based on an assessment of Tg(h, phi), we suggest that the Tg(h, phi) of miscible blends should be rationalized, additionally, in terms of the notion of a self-concentration and associated heterogeneous component dynamics.

New Routes to the Characterization and Prediction of Polymer Blend Properties

Using small-angle neutron scattering (SANS) results, pressure−volume−temperature (PVT) data from both polymer melts and blends, and experimentally determined critical temperatures, we employ the lattice Born−Green−Yvon (BGY) theory in the development of new routes for the characterization of polymer fluids and polymer blends. In particular, we focus on blends of polystyrene (PS) with poly(vinyl methyl ether) (PVME) and tetramethylbisphenol A polycarbonate (TMPC). In the first part of the paper we use the analytic expressions derived from the lattice BGY theory to fit the experimental data via three separate routes, using the different kinds of experimental data. In the second part of the paper we investigated the extent to which each of the methods lead to a thermodynamically consistent picture of the blend. Among other findings, we conclude that it is possible to use a relatively sparse data set and still produce a quantitative description of both pure component and blend behavior.

The glass transition of thin film polymer/polymer blends: Interfacial interactions and confinement

We examined the influence of film thickness and composition on the effective Tg of compatible thin film mixtures of polystyrene (PS) and tetramethylbisphenol-A polycarbonate (TMPC) on SiOx/Si substrates using spectroscopic ellipsometry. Our measurements reveal that while the Tg of TMPC films increased with decreasing film thickness, h, the effective Tg of thin film mixtures of PS and TMPC decreased with decreasing film thickness. In these mixtures, Tg was independent of film thickness at large h. We also found that while the Tg of bulk mixtures of TMPC/PS exhibited large negative deviations from additivity with composition, such deviations were negligible in the thin film mixtures. The thickness dependence of Tg is compared with theory.

Influence of the chemical structure of polycarbonates on the contribution of crosslinking and chain scissions to the photothermal ageing

The relative importance of crosslinking and chain scissions reactions involved in the photothermal ageing of polycarbonates is shown to depend on the chemical structure of the polymer. The orientation of these reactions is linked to the modifications of the chemical structure resulting from photolysis, photooxidation and thermooxidation. In this paper, the effects of crosslinking and chain scission of tetramethyl bisphenol-A polycarbonate (TMPC) are determined by size exclusion chromatography (SEC) and gel fraction measurements. These evolutions are correlated to the modifications of the chemical structure observed by FTIR spectroscopy. The presence of the four ortho-methyl substituants on the aromatic rings accounts for the difference in the photothermal ageing of TMPC compared to bisphenol-A polycarbonate (PC). Tetramethyl substitution inhibits photo-Fries rearrangements in TMPC, but in contrast these methyl groups involve crosslinks under irradiation and are the source of a higher oxidizability of TMPC compared to PC. A proposal for the various routes accounting for the crosslinking and the formation of the oxidation products in TMPC is reported in this paper.

Bulk Spinodal Decomposition Studied by Atomic Force Microscopy and Light Scattering

We report the first observation of bulk spinodal decomposition in polymer blends using atomic force microscopy (AFM). The fracture of a phase-separated thick film of tetramethyl bisphenol A polycarbonate (TMPC) and polystyrene (PS) is shown to induce a surface roughness that is resolvable by AFM. The resulting topography reproduces the spinodal morphology and is analyzed quantitatively. We investigate simultaneously the surfaces and bulk of the TMPC/PS films, a blend known to exhibit surface-directed spinodal decomposition. The structure factors obtained from a 2D-FFT of “bulk” AFM images and from time-resolved light scattering (LS) do not coincidethis is discussed in terms of the 2D (AFM) and 3D (LS) analysis involved. We finally compute general expressions relating 2D and 3D structure factors for a number of structures relevant to phase separation phenomena.

Blends of tribromostyrene copolymers

Copolymers of tribromostyrene (TBS) with styrene (S) and methyl methacrylate (MMA) were synthesized. The miscibility regions for blends of STBS copolymers with the homopolymers polystyrene (PS), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), tetramethyl bisphenol A polycarbonate (TMPC), as well as blends of MMA–TBS copolymers with poly(methyl methacrylate) (PMMA) were determined. Blends of MMA–TBS copolymers with styrene–methyl methacrylate (SMMA) copolymers and blends of both TBS copolymers with styrene–acrylonitrile (SAN) and styrene–maleic anhydride (SMA) copolymers were also investigated. Interaction energies for monomer unit pairs were calculated from the isothermal miscibility maps using the Flory–Huggins theory combined with the binary interaction model. The experimental phase separation temperatures were found to be similar to the spinodal temperatures predicted from the lattice-fluid theory of Sanchez and Lacombe using these interaction energies.

Phase separation of polymer blend TMPC/PS: dependence on blending method

Phase separation of polymer mixtures of tetramethyl bisphenol-A polycarbonate (TMPC) and polystyrene (PS) was studied by real-time small angle neutron scattering. Depending on the blending method (solution casting or melt mixing), samples are shown to exhibit different kinetics of spinodal decomposition and subsequent coarsening.

Short-range order in blends of polycarbonates with polystyrenes

The local structure of a series of blends of bisphenol-A polycarbonate (BPA-PC) and tetramethyl BPA-PC (TMPC) with various styrene-based polymers (poly(para-chlorostyrene), polystyrene, poly(meta-chlorostyrene) and poly(ortho-chlorostyrene)) has been investigated. Measurements on the D7 diffractometer at ILL were carried out at room temperature. We show that while the amorphous halo of TMPC is only slightly perturbed by blending, major differences are observed in all BPA-PC blends. We conclude that inter-chain correlations in BPA-PC blends are considerably altered compared to the pure component.

MISCIBILITY OF SOME POLYCARBONATES WITH POLYVINYL CHLORIDE AND CHLORINATED POLYVINYL CHLORIDE

The phase behavior of several polycarbonate homopolymers and copolymers blended with PVC and chlorinated PVCs (CPVCs) has been investigated. Tetrachlorobisphenol-A polycarbonate (TCPC) is miscible in all proportions with PVC and CPVCs containing up to70.2 wt% chlorine. CPVCs having chlorine contents greater than 70.2% (by weight) are immiscible with TCPC. Tetrabromobisphenol-A polycarbonate (TBPC) exhibits phase mixing with PVC and CPVCs; however, the high Tg of this polycarbonate (260°C) prevents adequate investigation of equilibrium phase behavior. Bisphenol-A polycarbonate (BPC), tetramethylbisphenol-A polycarbonate (TMPC), and hexafluorobisphenol-A polycarbonate (HFPC) form two-phase mixtures with the vinyl polymers. Microstructural differences in the CPVCs due to chlorination method (solution chlorination vs. slurry chlorination) have no effect on the miscibility results. Miscibility was observed in several copolycarbonate/CPVC blends and was found to be dependent on copolymer composition. Using a binary interaction, mean-field theory, segmental interaction parameters were estimated for repeat unit interactions. Based on the estimated interaction parameters, miscibility in these blends is primarily the result of intramolecular repulsive effects, rather than strong intermolecular attractive forces.

Interaction Parameter Predicted by Pressure-Volume-Temperature Properties of Miscible Polymer Blends

Expressions for Flory interaction parameter, χsc, were derived from the second derivative of the free energy of mixing by the following three equation of state theories: lattice fluid model of Sanchez and Lacombe [J. Phys. Chem., 80, 2352, 2568 (1976)], model of Flory, Orwoll, and Vrij [J. Am. Chem. Soc., 86, 3507 (1964)], and modified cell model by Dee and Walsh [Macromolecules, 21, 815 (1988)]. In each case, composition dependence of the characteristic pressure parameter, P*, was used to account for excess intermolecular interaction energy. The liquid state pressure-volume-temperature (PVT) properties of both pure components and mixtures of polystyrene and tetramethylbisphenol-A polycarbonate were measured at the weight fraction of polystyrene of 1/3 and 2/3, which were accordingly analyzed. The absolute values of χsc were always significantly larger than those obtained by small angle neutron scattering [H. Yang and J.M. O’Reilly, Mater. Res. Soc. Symp. Proc., 79, 129 (1987)] and diffusion [E. Kim et al., J. Polym. Sci., Polym. Phys. Ed., 33, 467 (1995)] measurements by a factor of 102. The PVT properties of blends misleadingly overstimate the enthalpic contribution, as also noted for the polystyrene (PS)/poly(vinyl methyl ether) mixture system by Ougizawa, Dee, and Walsh [Macromolecules, 24, 3834 (1991)].

Thermodynamics of mixing estimated by equation-of-state parameters in miscible blends of polystyrene and tetramethylbisphenol-A polycarbonate

Mixing thermodynamics in miscible blends of polystyrene (PS) and tetramethylbisphenol-A polycarbonate (TMPC) was investigated using liquid state pressure–specific volume–temperature ( P– v– T) properties of both pure components and mixtures. The equation-of-state theories used were (1) the lattice fluid model of Sanchez and Lacombe, (2) the model of Flory, Orwoll, and Vrij, and (3) the modified cell model suggested by Dee and Walsh. The composition dependence of characteristic pressure was first used to extract the interaction parameter (Δ P ∗) and Flory interaction parameter expressed in the second derivative of the free energy of mixing ( χ sc). It was found that the sign of χ sc was negative and the magnitude of it was always significantly larger than the values obtained by small-angle neutron scattering (Yang H, O'Reilly JM. Mater Res Soc Symp Proc 1987;79:129) and diffusion measurements (Kim E, Kramer EJ, Osby JO, Walsh DJ. J Polym Sci, Part B: Polym Phys 1995;33:467), indicating that the blend P– v– T properties grossly overestimate the attractive interaction. On the other hand, the χ sc predicted from the characteristic temperature was also large but had a positive sign. These results were similar to what had been found in PS/PVME blends by Ougizawa and coworkers (Ougizawa T, Dee GT, Walsh DJ. Macromolecules 1991;24:3834). While the thermal expansion coefficient began to increase as temperature is raised above the lower critical solution temperature (LCST), the volume contraction upon mixing was observed above as well as below the LCST. This observation implies that two dissimilar chains are packed together to form a certain stable stereo structure. We also note that the decreased change in core volume rather than the presence of large Δ P ∗ causes the volume contraction upon mixing.

A Dielectric Relaxation Study of the γ-Relaxation in Tetramethylbisphenol A Polycarbonate Plasticized by Tris(2-ethylhexyl) Phosphate

Dielectric relaxation spectroscopy (DR) was employed to study the dynamics of glassy tetramethylbisphenol A polycarbonate (TMBPA-PC) containing various amounts of tris(2-ethylhexyl) phosphate (TOP) added as diluent molecules. The present data confirm that the γ-relaxation dynamics, at constant frequency, shift to lower temperatures with increasing TOP content, an effect observed for the first time by dynamic mechanical measurements. This behavior of the γ-relaxation in TMBPA-PC plasticized by TOP is to be contrasted with that in bisphenol A polycarbonate (BPA-PC) plasticized by TOP. In the latter case, the γ-relaxation dynamics, at constant frequency, shift to higher temperatures with addition of TOP. These opposite trends of the γ-relaxation dynamics in two similar polycarbonates are surprising. However, the results can be rationalized by the coupling model.

Miscibility of polymer blends of poly(styrene‐co‐4‐hydroxystyrene) with bisphenol‐A polycarbonate

The miscibility of blends of bisphenol-A polycarbonate (BAPC) and tetramethyl bisphenol-A polycarbonate (TMPC) with copolymers of poly(styrene-co-4-hydroxystyrene) (PSHS) was studied in this work. It has been demonstrated that BAPC is miscible with PSHS over a region of approximately 45–75 mol % hydroxyl groups in the copolymer. TMPC has a wider miscible window than BAPC when blended with PSHS. The blend miscibility was considered to be driven by the intermolecular attractive interactions between the hydroxyl groups of the PSHS and the π electrons of the aromatic rings of both polycarbonates (PCs). As the FTIR measurements showed, after blending of BAPC with PSHS, there is no visible shift of the carbonyl band of BAPC at 1774 cm−1, whereas the stretching frequency of the free hydroxyl groups of the copoly- mers at 3523 cm−1 disappeared. The large positive values of the segment interaction energy density parameter Bst-HS calculated from the group contribution approach indicated that the intramolecular repulsive interaction may also have played a role in the promotion of the blend miscibility. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 639–646, 1999