Near infrared photon-assisted polymerization of advanced polymer composites.

Abstract

This dissertation describes a novel method to develop polymer composites using near infrared (NIR) photon-assisted polymerization and nanoscale reinforcement. We used multi-walled carbon nanotubes (MWNTs), reduced graphene oxide (RGO), and graphene nanoplatelets (GNPs) to make polymer composites, and explored in-situ NIR photon assisted heating of these nano carbons to enhance polymerization of the nanocarbon/polymer interface, thus achieving significant load transfer and improved vii mechanical properties. To specify, nano-carbon was dispersed into the polymer matrix by shear or evaporation mixing method to attain a uniform distribution in the prepared thin film composite. The thin film was exposed to NIR light during polymerization instead of conventional oven based heating. NIR was effectively absorbed by nano-carbons and also atoms from polymer molecule; the induced photo-thermal heat was transferred into the polymer matrix to induce polymerization of the composite and the covalent bonding between nano-carbons and polymer matrix at the interface. Scanning electron microscope (SEM), Raman spectroscopy, and RSA were used to evaluate the load transfer and mechanical strength of the polymerized composite samples. Investigating first the nanotube/polymer composites synergized by NIR photon-assisted polymerization, largeRaman shifts (20 cm -1 wavenumber for up to 80% strains) of the 2D band were recorded for the NIR light polymerized samples and an increase in Young's modulus by ~130%was measured for the 1 wt. MWNT/poly(dimethylsiloxane) (PDMS) composites. While at first it was thought that NIR radiation during polymerization heated the nano-carbons inside resulting in strengthening of the nano-carbon/polymer interface, it was seen after further experimentation with graphene reinforcements that other light induced bonding effects apart from heat were also responsible.Raman spectroscopy revealed that mixing graphene in polymer has a profound As a demonstration of applications, PDMS/RGO/PDMS sandwiched structure strain sensor, a demo application of the NIR photon-assisted polymerization was investigated. High sensitivity and high Gauge Factor (GF) are addressed. These results shown in this dissertation suggest that the NIR photon-assisted polymerization can be practically developed as a scalable nanomanufacturing technique to create large panels of advanced composites with strong interface and better mechanical properties compared to conventional oven based heating methods. It also suggests that it is possible to fabricate large-scale flexible smart device like high sensitivity strain sensors.xi