James F. Elman

E.s.c.a. studies of corona-discharge-treated polyethylene surfaces by use of gas-phase derivatization

Abstract Chemically specific gas-phase reactions have been used to tag corona-discharge-induced chemical species on the surface of polyethylene. These tag reactions provide distinct moieties that can be detected via e.s.c.a. to provide a surface count of induced species. Hydroxyl, epoxy, hydroperoxy, carboxylic acid and carbonyl populations are discussed as a function of corona energy input, time after treatment and water washings.

An e.s.c.a. study of the gas-phase derivatization of poly(ethylene terephthalate) treated by dry-air and dry-nitrogen corona discharge

Abstract Gas-phase derivatization has been used along with e.s.c.a. to determine corona-discharge-induced chemical species on poly(ethylene terephthalate) (PET). Dry-air and dry-nitrogen coronas were studied. We showed that: (1) if the corona discharge treatment (CDT) power level is kept low enough, few water-soluble species are created; (2) 4% of oxygen is added to the surface with dry-air corona; (3) 75% of the oxidation products are identified as hydroperoxy, epoxy, hydroxyl, carboxylic acid and isolated carbonyl species (with hydroxyl and isolated carbonyl the prevalent species). Short-term time-dependent ageing studies show a one-to-one correspondence between the decrease in hydroperoxy species and the increase in hydroxyl and isolated carbonyl moieties. Reaction sequences are proposed to explain these data. At longer times these surface populations decrease. In general, the results from nitrogen coronas and dry-air coronas are similar.

Characterization of biaxially-stretched plastic films by generalized ellipsometry

Abstract An ellipsometric method for determining the optical constants and optic axis orientations of a biaxially stretched plastic film is described. This technique works by making angularly resolved generalized anisotropic ellipsometric measurements in transmission and reflection and does not require special or multiple sample azimuthal orientations. The measured data is then subjected to a model regression procedure which can account for the propagation of multiple beams through biaxially anisotropic layers. The results are consistent with Abbe refractometer measurements. The ellipsometric results near normal incidence also indicate that the in-plane optic axes are twisted through the layer.

IR ellipsometry studies of polymers and oxygen plasma-treated polymers

Abstract An infrared variable angle spectroscopic ellipsometer (IR-VASE) was used to study organic polymers in the infrared (2.5–14 μm wavelength) spectral region. For the analysis of thin film polymers IR spectroscopic ellipsometry has greater sensitivity over traditional FTIR spectroscopy providing an exciting way to characterize these materials optically. The IR-VASE used in this study is of high accuracy, rotating polarizer, rotating compensator ellipsometer that uses an FTIR spectrometer as a light source. The IR-VASE was used to measure the infrared optical constants of various polymers in both solid and liquid form. These optical constants were then used to model the percentage of water in a thin film of gelatin and the percentage of residual solvent in a thin film of silicone. In addition, the IR-VASE provided a sensitive measurement of silicone chemistry and chemical changes caused by exposure to an oxygen plasma.

Optical properties of solvent-cast polarizer films for liquid-crystal displays: A viscoelastic modeling framework

Abstract— Many of the films used in polarizer assemblies in LCDs (e.g., triacetyl cellulose or TAC) are produced by a solvent-casting process, which is known to impart optical anisotropy to the film expressed as finite out-of-plane birefringence. This feature of the film could have a significant impact on the optical performance of the display and it needs to be accounted for in any compensation scheme for the LC cell. This paper reviews the origin of this optical anisotropy, and it presents a viscoelastic model that links this property to the solvent-casting process and to some key material parameters. The model results are compared with experimental data generated for polystyrene films cast from toluene, and generally good agreement is demonstrated.

Effect of molecular weight blending on the fracture energy and morphology of the semicrystalline polymer poly(1,4-dimethylene-trans-cyclohexyl suberate)

Abstract Fracture studies were made on bimodal molecular weight blends of poly(1,4-dimethylene-cyclohexyl suberate) (MCS), where small additions of low-molecular polymer to the higher molecular weight material drastically decreased the crack propagation energy. The data are rationalized in terms of exclusion of the low-molecular weight fraction from the crystalline matrix during crystallization. These blends have a unique minimization of spherulite size as a function of composition. This effect is explained in terms of changes of surface free energy of crystal nuclei as a function of molecular weight. Fracture morphology shows almost total brittle fracture of the blends. This result corresponds to the drastic decrease in propagation energy in these blends and suggests that most of the data showing a high propagation energy are due to plastic deformation. The temperature dependence of the energy to propagate a crack, G p , is explained in terms of a local-deformation (thermally activated) model. The activation energies obtained, as a function of blending and annealing conditions, are discussed in terms of linear damage theory.

P-108: Birefringence Dispersion of Polymer Films As Applied to Optical Compensation in LCD

Minimizing color shift effects in a liquid crystal display (LCD) requires close attention to the optical dispersion of compensation layers used to increase the contrast ratio and viewing angle of the display. This paper describes our attempt to systematize and characterize the birefringence dispersion of solvent-cast polymer films and relate it to the “native” out-of-plane birefringence (Δnth) of the polymer and its structure. Results for a wide range of polymers show general correlation between the dispersion parameter DPΔn [≡Δn(450)/Δn(590)] and Δnth. for all positively birefringent polymers, DPΔn is always > 1, suggesting “normal” dispersion at any level of Δnth, while for negatively birefringent polymers DPΔn > 1 only when |Δnth| > ∼0.003. Below this critical value, DPΔn < 1, i.e., the polymer is reverse-dispersive. The results are explained in terms of the Cauchy coefficients for the corresponding polymers, and they suggest that the dispersion of birefringence cannot be controlled independently of the birefringence of the polymer film.

P‐145: Polymer C‐Plate Retarders: History and Future

A brief review is given of the surprisingly long history of C plates made from polymeric materials. Previous work dating from the early 1900s is discussed. A new class of amorphous polymers is identified, and aspects of their structure, properties, and performance are shown.

P-120: Optical Properties of Solvent-Cast Polarizer Films for Liquid Crystal Display: A Viscoelastic Modeling Framework

The optical properties of polarizer films in LCD are critical to the optical performance of the display. Solvent-cast cellulosic films (e.g., triacetyl cellulose or TAC) are used in conventional polarizer assemblies, in part, for their high transmission and relatively low optical retardation. However, even low-birefringent materials such as TAC film possess some finite level of residual out-of-plane retardation that needs to be accounted for in various compensation schemes for the display. This paper reviews the origin of this optical anisotropy, and it describes a viscoelastic model that links this property to the solvent-casting process.

Extension of the chain-end free volume theory for predicting the Tg−M−1n relationship for homopolymer bimodal blends

The chain-end theory of free volume has been extended to describe the Tg−M−1n behaviour of bimodal blends of homopolymers. The theory provides an equation of the form: Tg=Tg∞−KMA1X+(1−X)PX+(1−X)QMAMB where P = αBαA is the ratio of free volume expansion for the individual chain-ends and Q = (ϱBϱA)(θBθA) where ϱ is the density and θ is the chain-end free volume of each component. X is the weight fraction of component A. The equation fits experimental data for the Tg−M−1n relationship in two polycarbonate and two polystyrene blends.