Investigations of the Correlation between the Preparation Method and the Properties of Anilinic Derivative Functionalised Polymer Thin Films for Non-Linear Optical Applications

Abstract

This paper presents a study of two copolymers, maleic anhydride and methylmethacrilate/maleic anhydride and vinyl benzyl chloride, functionalised with polar chromophoric groups such as 2,4 dinitroaniline. Thin films have been prepared by vacuum evaporation and spin coating methods on silicon and glass substrates. UV-VIS, FTIR, XRD and Photoluminescence Spectroscopy have been used to comparatively investigate the effect of the preparation method on the properties of the thin films obtained with functionalized copolymer. SEM has evidenced differences in the morphologies of the layers suggesting a degradation of the polymeric chain during the evaporation process to fragments that conserve unchanged the chromophoric group. This explains the presence of two types of non-linear phenomena, the second harmonic emission and two-photon luminescence emissions for both vacuum evaporated and spin coated films.

Organic Semiconductors for Non-Linear Optical Applications

“…We have studied two polymeric structures introduced in Figure 28, P1: MA-CMS-DNA synthesised by the copolymerisation of maleic anhydride (MA) with vinyl benzil chloride (MA-CMS) and subsequent functionalisation with 2, 4-dinitroaniline (DNA) and P2: MA-MMA-DNA synthesised by the copolymerisation of maleic anhydride and methylmethacrilate (MA-MMA) and subsequent functionalisation with 2, 4-dinitroaniline (DNA). Functionalised copolymers have been synthesised in a two-stages process: (1) polymerisation by precipitation initiated by azoizobutylnitrile in toluene at 80 ο C for 2 h; (2) polymers grafting with ortho-, para-aniline derivatives in DMF by opening and closing of the anhydridic cycle at 120°C for 2 h [50][51][52]29].…”

“…Thin films of grafted copolymers P1 and P2 have been prepared using different methods on different substrates like glass, cleaned in acetone, and etched/etched single silicon wafers, successively cleaned ultrasonically with acetone, hydrofluoric acid and distillate water [50].…”

“…Polymeric films have been deposited from solution by spin coating in a process involving two steps: (1) preparation of polymer solution in an adequate solvent; (2) deposition of the film by solution spreading (spinning time 9 s for P1 and 3 s for P2; rotational speed 0.75 krpm for P1 and 0.65 krpm for P2 [50]) followed by homogenisation (spinning time 20 s for P1 and 10 s for P2; rotational speed 2.75 krpm for P1 and 1.70 krpm [50]). We have selected DMF as solvent, because it is characterised by a low evaporation rate and strong interactions with the native layer of SiO 2 covering the Si surface.…”

“…Polymeric thin films have also been prepared by vacuum evaporation at a temperature of 100-110°C for P1 and 80-90°C for P2 and a pressure between 1.2-1.9×10 -5 mbar for P1 and 1.0-1.7×10 -5 mbar for P2 [50]).…”

“…We have studied two polymeric structures introduced in Figure 28, P1: MA-CMS by the copolymerisation of maleic anhydride with vinyl benzil chloride (MA-CM functionalisation with 2,4-dinitroaniline (DNA) and P2: MA-MMA-DNA s copolymerisation of maleic anhydride and methylmethacrilate (MA-MMA functionalisation with 2,4-dinitroaniline (DNA). Functionalised copolymers have a two-stages process: (1) polymerisation by precipitation initiated by azoizobutyl 80  C for 2 h; (2) polymers grafting with ortho-, para-aniline derivatives in DM closing of the anhydridic cycle at 120C for 2 h [50][51][52]29]. Thin films of grafted copolymers P1 and P2 have been prepared using different m substrates like glass, cleaned in acetone, and etched/etched single silicon wafers, s ultrasonically with acetone, hydrofluoric acid and distillate water [50].…”