Abstract
Aromatic polyurea (PU) films were fabricated by vapor deposition polymerization using 4,4′-diphenylmethane diisocyanate and 4,4′-diaminodiphenylmethane. To investigate the influence of preparation conditions upon decay of optical second harmonic generation (SHG) after poling, two kinds of films were deposited: PU(No. 1) involving less residual isocyanate groups and PU(No. 2) with a smaller molecular weight and more residual isocyanate groups. PU(No. 2) showed significant decay, while PU(No. 1) did not. The results of IR spectrometry and differential scanning calorimetry indicated that the formation of urea bonds during poling of as-deposited films was due to reaction of the isocyanate groups with amino groups in PU(No. 1) and with water in PU(No. 2). We ascribed the SHG decay in PU(No. 2) to free volume formation by elimination of or plasticizing by CO2 generated during the above reaction, and/or to the smaller molecular weight.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
