Wojciech Fabianowski

Active metals prepared in liquid ammonia. Zinc and tin-promoted synthesis of β-hydroxyesters, homoallylic and homopropargylic alcohols

Active zinc and tin powder can be prepared by reduction of ZnCl2 and SnCl2 with sodium in tetrahydrofuran-liquid ammonia mixtures of various compositions. The activity of the reduced zinc depends on concentration of ammonia in the reaction medium. Zinc (A) prepared in liquid ammonia (Method A) was much less active then zinc (B) prepared in THF containing 10–20 volume % of liquid ammonia (Method B). The X-ray powder diffractometry data suggested that zinc (B) was less crystalline then zinc (A). The Reformatsky and Barbier type reactions of carbonyl compounds with α-bromoesters, allylic and propargylic bromides in the presence of Zn or Sn prepared by method B gave the corresponding β-hydroxyesters, homoallylic and homopropargylic alcohols in good to excellent yields.

PDLC optical displays with LC encapsulated in polymerized vesicles

Optical displays with polymer dispersed liquid crystals have a diffused interphase region between LC droplets and polymer, composed mostly from LC swelling polymer matrix. This interphase region has a different optical characteristic comparing to the bulk material inside LC droplets. For the purpose of reducing volume occupied by the interphase region, we have adopted a procedure used in the liposome reserach. LC with dichroic dye was encapsulated in the vesicles formed by the polymerizable amphiphilic compound Dimethyldioctadecylammonium Methacrylate. After encapsulation, vesicles with LC/dye system inside were UV polymerized and dispersed in the poly(vinyl alcohol) PVA matrix. Changes of the optical transmittances of obtained thin films versus applied electrical field showed symmetrical s-shaped curves but low transmittance changes.

Flexible humidity sensors with polymer sorption layer

This paper presents humidity sorption sensors with eight different polymer coatings. After the introduction of sensor construction, a presentation of tested sorption laters and measurement system is provided. Finally, the results are presented and discussed as well as validation tests are described. Two most suitable coatings are chosen.

Growth control of polymer films deposited on the planar waveguide

Propagation of the light in a waveguide structure may be easily disturbed by the change of a cover. In this study multilayers of 7-octenylotrichlorosilane have been investigated as cover films. The multilayer films were deposited on the planar waveguide by self-assembly, followed by a UV illumination and repeated self-assembly processes. A growth control of the deposited films was performed by the generalized method of an m-line spectroscopy. M-line spectroscopy is one of the most sensitive methods of investigations of the cover materials parameters.

Parameters of thin films deposited on planar waveguides

Using the method of m-line spectroscopy [1] it is possible to determine parameters (thickness and refractive index) of thin films deposited on planar waveguides through indirect measurement of changes of coupling angle to the waveguide. The subject of the study were thin organic films deposited on waveguides by casting diluted polymerizable solutions, and by spin-coating thin polyimide films. These films are developed as active coatings in waveguide sensors. Numerical calculations (applied for three-layer structures) after modification to a four-layer structure allows for determining the parameters of thin films.