Authors: Yunlong Zhao
Source: Scholarworks (University of Massachusetts Amherst) (article, 2021-04-01)
Field: Chemistry — Spectroscopy

Characterization of Highly Heterogeneous Heparin-Protein Complexes Using Novel Mass Spectrometry-Based Approaches Block copolymers (BCPs), due to their ability to self-assemble into periodic nanoscale morphologies, have been extensively studied over the past few decades. The thermodynamic parameters governing self-assembly of BCPs generally leads to periodic morphologies with characteristic length scales ranging from 10 to 100 nm. Several applications have been demonstrated utilizing BCPs as a template for the fabrication of nanostructured materials. Fabricating structures beyond the 10-100 nm range, remains a challenge and constitutes one of the goals of the proposed research. This dissertation is divided into two parts. The first focuses on the sub 10 nm length scale, when by chemically converting one of the blocks of the BCP, segmental interactions can be made extremely non-favorable, enabling smaller size scale structure to be achieved. The second is related to the study of brush block copolymers (BrBCPs) that can produce structured with characteristic length scales that can span from the sub-10 nm to 100s of nm. In first part, poly (styrene-<em>b</em>-solketal methacrylate) (PS-<em>b</em>-PSM) was investigated to generate the highly ordered microphase separated structures with deep sub 10 nm period. This novel BCP contains the solketal group which can be hydrolyzed readily into the glyceryl group in dry state under acidic conditions. The phase-mixed PS-<em>b</em>-PSM BCPs were forced into highly ordered lamellae microdomain of poly(styrene-<em>b</em>-glyceryl methacrylate) (PS-<em>b</em>-PGM) by substantial increase of Flory-Huggins segmental interaction parameter by the acid triggered hydrolysis reaction. The weakly segregated microdomains of the PS-<em>b</em>-PSM was successfully driven into the strongly segregated regime microdomains of the PS-<em>b</em>-PGM. Highly ordered lamellae microdomain of the PS-<em>b</em>-PGM with deep sub 10 nm domain size was achieved in thin film by conversion in dry state from the precursor PS-<em>b</em>-PSM thin films. The lamellae microdomain orientation was controlled into perpendicularly oriented to the substrate by novel design of conversion BCP thin film in a gradient manner. In second part, BrBCPs blends containing homopolymers in bulk and thin films were investigated. BrBCPs have been achieved great attention to achieve microphase separated structures with extremely large microdomain size over 100 nm readily compared to the conventional linear BCP. Its unusual rigid-like structure from the densely-grafted side chains to the backbone can prohibit it from the chain entanglement so as to provide the fast kinetics of the self-assembly. By adding homopolymers to the BrBCPs, the microdomain size was further increased. The morphologies and microdomain size of BrBCPs blends with homopolymers were studied using small angle x-ray scattering measurement. Perdeuterated homopolymers were used to detect the exact location and distribution of homopoymers in thin films by performing neutron reflectivity. It was evaluated of the distance and the interfacial width of microdomains of BrBCP blends by mixture of homopolymers as a function of the size and the amount of homopolymers. Mass spectrometry ; Chemistry ; Characterization (materials science) ; Chromatography ; Nanotechnology ; Materials science Mass Spectrometry Techniques and Applications