Polymeric films evaluation

Evaluation of Polymeric Films for Oak Ridge National Laboratory, Report... 

When optical anisotropies form spontaneously in the polymeric film during deposition, the situation is more complicated. Significant effects are observed in optical and spectroscopic properties, such as LED emission [17] and waveguide propagation [45-50,52,64], For these films, accurate evaluation of the optical constants is more difficult and must be based on variable incidence angle measurements, as in the case of surface plasmon resonance [45-47], waveguide propagation [48-50,52], ellipsometry [64,67], and reflectance/transmittance [68]. 

The enzymatic activity of a-chymotiypsin was evaluated in composites of poly(methyl metacrilate) with different carbon materials [91] demonstrating that the incorporation of SWCNTs into enzyme-polymer composites results in active and stable polymeric films. The release of the protein from the composite was evaluated measuring the enzymatic activity in the supernatant in contact with the composite. The results showed that in the case of SWCNTs the leaching of the protein from the composite was lower. This fact was attributed to the imion of the protein to the CNTs. The effect of other polymers such as polystyrene and poly(lactic acid) was also analyzed and the leaching of the protein was significant in the absence of SWCNTs. Only the hydrophobic ones (poly(methyl metacrilate)... 

Photoinitiator concentration 1 mol% of benzophenone moieties in the HDDA/APDG mixture. Irradiation performed by a medium-pressure linear (15 cm) Hg lamp (5(X) W) on a 10 pm thick liquid film between two NaCl discs located at a distance of 20 cm Half-time of the process as determined by IR spectroscopy Polymerization rate evaluated at ti/2 and expressed as % conversion over time... 

Radebaugh GW, Murtha JL, Julian TN, Bondi JN. Methods for evaluating the puncture and shear properties of pharmaceutical polymeric films. Int ] Pharm 1988 45 39 6. 

Experimental details.1503 A mixture of the monomer 579 (1 3 mg) and a photoinitiator ( 3 wt%) in a sample (open-air) cell was irradiated with a high-pressure mercury discharge lamp (200 W) (Figure 3.11). In order to prevent evaporation of the monomer, the cell was covered with a thin poly(ethylene terephthalate) film. The extent of polymerization was evaluated by differential photocalorimetry. 

Figures 32a and 33 show the evaluation of the electrooptic Pockels coefficient 1-33 of our polymeric films during typical PEP cycles at room temperature. These curves were obtained as explained before by continuously recording the lock-in signal modulated at Q near the largest incidence TM mode which gives the direct measurement of An. When the measuring ac ( 3) and poling dc (Eg) electric fields are applied simultaneously to the polymer film, the An (z is equivalent to 3) variation is given by (Eq. 29) ...

Adhesion between the polymeric film and substrate is a major concern. Poor adhesion could result in flaking or peeling of the coating from the substrate core. Moisture could accmnulate at the film-substrate interface and compromise the mechanical protection provided by the coating. Polymer adhesion is related to both film-substrate interfacial interactions and internal stresses within the film. Polymer adhesion can be evaluated by peel tests or butt joint tests. Apart from the specific properties of the polymers, excipients used in tablet formulations can influence film-tablet adhesion. Since adhesion between a polymer and the tablet smface is due primarily to hydrogen bond formation, hydrophobic agents may decrease adhesion by... 

The formation and characterization of ultrathin film formed by poly(3-amino-benzoic acid) (PABA) was carried out by Sriwichai et al. [55] using ESPR for the development of immunosensor to detect human immunoglobulin G. With the aid of simultaneous measurements of SPR and CV it has been become possible to calculate the thickness and dielectric properties of a polymeric film, allowing that immunosensor responses can be related to its surface morphology. Another ESPR biosensor also based on PABA was developed by Baba et al. [56] to detect adrenaline. The polymer acts as a specific reaction site for adrenaline, presenting different electrochemical and SPR responses to those for uric and ascorbic acids, which are major interferences of the catecholamine studied. The two techniques were used to evaluate the electrodeposition of PABA and to obtain the calibration curves and the detection limit was set to 100 pmol... 

On the other hand, the optical anisotropic properties of all the samples prepared were also evaluated. Optical anisotropy is a photo-induced birefringence in the polymeric films resulting from a reorientation of the azobenzene moieties. Generally, linearly polarized light is used to provoke a trans-cis isomerisation followed by a molecular reorientation and a cis-trans isomerisation. The absorption and reorientation sequence will be repeated until the azobenzene molecules dipole moment lies in a direction which is perpendicular to the polarisation direction of the writing beam. In this way, optical anisotropy can be induced in the films [7]. 

In numerous applications of polymeric materials multilayers of films are used. This practice is found in microelectronic, aeronautical, and biomedical applications to name a few. Developing good adhesion between these layers requires interdiffusion of the molecules at the interfaces between the layers over size scales comparable to the molecular diameter (tens of nm). In addition, these interfaces are buried within the specimen. Aside from this practical aspect, interdififlision over short distances holds the key for critically evaluating current theories of polymer difllision. Theories of polymer interdiffusion predict specific shapes for the concentration profile of segments across the interface as a function of time. Interdiffiision studies on bilayered specimen comprised of a layer of polystyrene (PS) on a layer of perdeuterated (PS) d-PS, can be used as a model system that will capture the fundamental physics of the problem. Initially, the bilayer will have a sharp interface, which upon annealing will broaden with time. 

---