TY - BOOK

T1 - Surface modification with germanium-based photoinitiators and surface-mediated photopolymerization techniques

AU - Müller, Matthias

N1 - no embargo

PY - 2024

Y1 - 2024

N2 - Over the last decades, surface science has witnessed an ever more increasing interest in surface-modification and functionalization techniques across academic and industrial sectors. Especially the grafting-from approach, giving access to smart materials and surfaces, continues to drive innovation also in biomedical fields, in terms of drug release systems, tissue engineering, wound healing, diagnostics, protein binding and many more. This technique relies on the covalent attachment of an initiating species at a surface, which is then utilized to deliver reactive sides like radicals or ions, upon heat or light exposure. This is then followed by surface-initiated polymerization reactions, resulting in a fixed polymer brush system. Among those methods, especially light induced processes have received much attention due to the fast reaction rates, low cost as well as the spatial and temporal controllability. Hence, huge progress has been made so far in order to introduce type I and type II photoinitiators or other photo-sensitive molecules to different material surfaces. In order to provide new perspectives in the field of grafting-from techniques, especially for usage in biomedical applications, a highly efficient, low-toxic and visible light sensitive class of photoinitiators, based on germanium (trisacylgermanes), were immobilized onto inorganic surfaces, including silicon wafers, optically polished quartz plates and spherically shaped silica nanoparticles. Those moieties were then exploited to initiate a radical chain-growth reaction from those surfaces via visible light illumination. By choice of functional monomers, polymer brushes with anti-adhesive, hydrophilic and fluorescent features were produced onto silicon wafers and quartz plates, also in spatially resolved and combined manners. The derived polymer mono-layers were then investigated in respect to certain properties and brush-thicknesses using a set of characterization methods, including spectroscopic ellipsometry, XPS, UV-Vis, contact angle -and fluorescence measurements. Taking photo-initiator functionalized nanoparticles into account, hybrid organic-inorganic nanomaterials were synthesized, comprising a 6 to 12 nm thick polymeric shell around the SiO2-core. Moreover, the polymer content, the grafting-yield as well as the initiator and polymer grafting-density will be discussed in detail herein. Another highlight in this thesis is the presentation of the first example of a so-called surface-initiated radical promoted cationic photopolymerization, which was achieved via the oxidation of photoinitiator formed radicals by iodonium salts. The derived germanium centred cation allowed then to remove the restriction to radically polymerizable monomers by expanding the selection with cationic polymerizable counterparts, like vinyl ethers and epoxides, hence opening up new perspective for grafting-from processes. For this method, the emphasis was placed on the overall proove of principle.

AB - Over the last decades, surface science has witnessed an ever more increasing interest in surface-modification and functionalization techniques across academic and industrial sectors. Especially the grafting-from approach, giving access to smart materials and surfaces, continues to drive innovation also in biomedical fields, in terms of drug release systems, tissue engineering, wound healing, diagnostics, protein binding and many more. This technique relies on the covalent attachment of an initiating species at a surface, which is then utilized to deliver reactive sides like radicals or ions, upon heat or light exposure. This is then followed by surface-initiated polymerization reactions, resulting in a fixed polymer brush system. Among those methods, especially light induced processes have received much attention due to the fast reaction rates, low cost as well as the spatial and temporal controllability. Hence, huge progress has been made so far in order to introduce type I and type II photoinitiators or other photo-sensitive molecules to different material surfaces. In order to provide new perspectives in the field of grafting-from techniques, especially for usage in biomedical applications, a highly efficient, low-toxic and visible light sensitive class of photoinitiators, based on germanium (trisacylgermanes), were immobilized onto inorganic surfaces, including silicon wafers, optically polished quartz plates and spherically shaped silica nanoparticles. Those moieties were then exploited to initiate a radical chain-growth reaction from those surfaces via visible light illumination. By choice of functional monomers, polymer brushes with anti-adhesive, hydrophilic and fluorescent features were produced onto silicon wafers and quartz plates, also in spatially resolved and combined manners. The derived polymer mono-layers were then investigated in respect to certain properties and brush-thicknesses using a set of characterization methods, including spectroscopic ellipsometry, XPS, UV-Vis, contact angle -and fluorescence measurements. Taking photo-initiator functionalized nanoparticles into account, hybrid organic-inorganic nanomaterials were synthesized, comprising a 6 to 12 nm thick polymeric shell around the SiO2-core. Moreover, the polymer content, the grafting-yield as well as the initiator and polymer grafting-density will be discussed in detail herein. Another highlight in this thesis is the presentation of the first example of a so-called surface-initiated radical promoted cationic photopolymerization, which was achieved via the oxidation of photoinitiator formed radicals by iodonium salts. The derived germanium centred cation allowed then to remove the restriction to radically polymerizable monomers by expanding the selection with cationic polymerizable counterparts, like vinyl ethers and epoxides, hence opening up new perspective for grafting-from processes. For this method, the emphasis was placed on the overall proove of principle.

KW - Surface modification

KW - Germanium-based photoinitiators

KW - Grafting-From technique

KW - Initiator immobilization

KW - Surface-initiated photopolymerization

KW - Polymer brushes

KW - Radical promoted cationic photopolymerization

KW - Oberflächenmodifikation

KW - Germanium-basierte Photoinitiatoren

KW - Grafting-From-Technik

KW - Initiator-Immobilisierung

KW - Oberflächen-initiierte Photopolymerisation

KW - Polymerbürsten

KW - Radikalisch vermittelte kationische Photopolymerisation

U2 - 10.34901/mul.pub.2024.203

DO - 10.34901/mul.pub.2024.203

M3 - Doctoral Thesis

ER -