Nanomechanical Properties of Polymer-Grafted Nanoparticle Ultrathin Films

Polymer thin films have recently become one of the most emerging research areas due to their profuse applications in energy storage, flexible electronics, and photonics. The mechanical response of polymer thin films is crucial in defining a high-performance device encompassing the film’s durability, bondability, and flexibility. In the past few decades, the mechanical properties of nanoparticle-filled polymer thin films have been studied rigorously, suggesting that the inclusion of nanoparticles in the polymer matrix enhances the elastic modulus of thin films. However, there’s still a window of opportunity for an intensive study of the process-morphology-property (PMP) relationship for polymer-grafted nanoparticle (PGNP) thin films based on the particle size, loading percentage, the molecular weight of the grafted polymer, and film thickness. This research investigates the elastic modulus of polymethyl methacrylate grafted nanoparticle (PMMA-g-SiO2) thin films as a function of thickness and processing conditions. PGNPs of 15nm core diameter with grafted PMMA chains of molecular mass (59.4 kg/mol) and grafting density (0.44/nm2) were dispersed in tetrahydrofuran (THF) solution to produce thin films of varying thickness ranging from 45nm to 200nm. The nanoparticle distribution throughout the film thickness and surface roughness were studied using atomic force microscopy. The PMMA (64.5kg/mol) films with similar thickness ranges were analyzed to compare the effect of PGNPs on the elastic modulus for both as-cast and thermally annealed conditions, evaluated through strain-induced elastic buckling instability for mechanical measurements (SIEBIMM) technique. This study was further extended by blending the PMMA-g-SiO2 nanoparticles at 5 %wt. loading to block copolymer (BCP) matrix (PS-b-PMMA) (45-b-48 kg/mol) to investigate the effects of the nanofiller inclusions on the elastic modulus of BCP film of 150nm thickness. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) was used to investigate the ordering of the nanoparticle-filled block copolymer thin film upon thermal annealing for different periods. The elastic modulus was enhanced for the PGNP thin films with thickness in the ultrathin regime (<100nm). Moreover, thermal annealing led to a further increase in the elastic modulus. The mechanical response of the polymer nanocomposite was evaluated to explore the viability of PGNP inclusions as compared to the pure BCP film.

Name thesis:degree_name

Master of Science in Mechanical Engineering

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Houston

Year dc:date.issued

2024

Author dc:creator

• Mohammed, Masiuddin Muzzammil

Advisors dc:contributor.advisor

• Ghasemi, Hadi
• Karim, Alamgir

Committee member dc:contributor.committeemember

• Ryou, Jae-Hyun

• Ultrathin Films, PGNP, PMMA, SIEBIMM, BCP, PS, Elastic Modulus

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10657/17687

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/17687