TY - BOOK

T1 - Study of low migratable photopolymer networks

AU - Sahin, Melahat

N1 - embargoed until 19-01-2023

PY - 2018

Y1 - 2018

N2 - Photo-crosslinked materials have widespread applications ranging from medical devices to food packaging. However, migration of chemicals from polymeric networks is a critical issue which does not only limit the use of these materials in many potential application fields but also pose the risk of serious health problems. The aim of this thesis is the preparation of low migratable 3-D polymer networks by taking advantage of light-induced reactions as well as the analysis of the main parameters that influence the network formation and the related network properties (e.g. tensile strength). In the first part of this thesis, the influence of selected thiol and alkene structures on the network properties of thiol-ene based photopolymers were investigated by photopolymerizing cycloaliphatic and linear thiols with an allyl monomer or its acrylic counterpart. FT-IR spectroscopy was used to evaluate the crosslink kinetics and allowed a comparison of the step growth and chain growth mechanism of the two different systems. Furthermore, mechanical and thermal measurements as well as solid state NMR measurements were conducted to correlate network properties with macroscopic behaviour. In the second part of this thesis, thiol-ene networks were prepared using low migratable thiol components. Natural rubber (NR) latex was used as the alkene component due to its technological relevance in the production of medical gloves and other products used in medical and nonmedical application. Three different systems of low migratable thiol crosslinker were used. In the first approach, commercially available multifunctional thiols with a high molecular weight were used as crosslinker. The second concept aimed at the synthesis of oligomeric siloxane based thiols, which were then applied as crosslinkers in the UV induced crosslinking of NR. The third system involved the application of thiol functionalized silica and zeolite particles as crosslinkers. Covalent attachment of the thiol groups on the particle’s surface was obtained by a convenient silanization method. The use of either functional inorganic nanoparticles or high molecular weight thiols was expected to decrease the extractability of crosslinker from UV-cured NR samples compared to conventionally applied low molecular weight crosslinkers. Thus, these strategies are promising ways to enhance the skin compatibility and biocompatibility of photopolymers (e.g. applied in medical products). Migration of crosslinkers was examined by using a Soxhlet extraction procedure, whilst the extracts were characterized by elemental analysis. Furthermore, tensile tests and swelling measurements were conducted to characterize the mechanical properties of photochemically crosslinked NR films. The third part of this work focuses on low migratable photoinitiators. The first section describes the immobilization of trialkoxysilyl functionalized photoinitiators onto the surface of silica particles. Immobilized photoinitiators are expected not to migrate out of the polymer network, which is a desired property in the design of photocurable coatings and medical products. The photoactive silica particles obtained under various experimental conditions were characterized and used as initiators in a thiol-ene resin. Network evolution of the resins initiated by the photoactive silica particles and their commercially available counterparts was investigated by FTIR spectroscopy. Migration of photoinitiators was investigated using a Soxhlet extraction procedure. The amount of extractable photoinitiator and cleavage products was evaluated by elemental analysis. In a second approach, a low migratable photoinitiator with a vii polymerizable group was used in the UV-curing of NR latex via thiol-ene reaction. Mechanical properties of the cured samples and migration behaviour of the photoinitiator were compared with the samples prepared with the parent initiator.

AB - Photo-crosslinked materials have widespread applications ranging from medical devices to food packaging. However, migration of chemicals from polymeric networks is a critical issue which does not only limit the use of these materials in many potential application fields but also pose the risk of serious health problems. The aim of this thesis is the preparation of low migratable 3-D polymer networks by taking advantage of light-induced reactions as well as the analysis of the main parameters that influence the network formation and the related network properties (e.g. tensile strength). In the first part of this thesis, the influence of selected thiol and alkene structures on the network properties of thiol-ene based photopolymers were investigated by photopolymerizing cycloaliphatic and linear thiols with an allyl monomer or its acrylic counterpart. FT-IR spectroscopy was used to evaluate the crosslink kinetics and allowed a comparison of the step growth and chain growth mechanism of the two different systems. Furthermore, mechanical and thermal measurements as well as solid state NMR measurements were conducted to correlate network properties with macroscopic behaviour. In the second part of this thesis, thiol-ene networks were prepared using low migratable thiol components. Natural rubber (NR) latex was used as the alkene component due to its technological relevance in the production of medical gloves and other products used in medical and nonmedical application. Three different systems of low migratable thiol crosslinker were used. In the first approach, commercially available multifunctional thiols with a high molecular weight were used as crosslinker. The second concept aimed at the synthesis of oligomeric siloxane based thiols, which were then applied as crosslinkers in the UV induced crosslinking of NR. The third system involved the application of thiol functionalized silica and zeolite particles as crosslinkers. Covalent attachment of the thiol groups on the particle’s surface was obtained by a convenient silanization method. The use of either functional inorganic nanoparticles or high molecular weight thiols was expected to decrease the extractability of crosslinker from UV-cured NR samples compared to conventionally applied low molecular weight crosslinkers. Thus, these strategies are promising ways to enhance the skin compatibility and biocompatibility of photopolymers (e.g. applied in medical products). Migration of crosslinkers was examined by using a Soxhlet extraction procedure, whilst the extracts were characterized by elemental analysis. Furthermore, tensile tests and swelling measurements were conducted to characterize the mechanical properties of photochemically crosslinked NR films. The third part of this work focuses on low migratable photoinitiators. The first section describes the immobilization of trialkoxysilyl functionalized photoinitiators onto the surface of silica particles. Immobilized photoinitiators are expected not to migrate out of the polymer network, which is a desired property in the design of photocurable coatings and medical products. The photoactive silica particles obtained under various experimental conditions were characterized and used as initiators in a thiol-ene resin. Network evolution of the resins initiated by the photoactive silica particles and their commercially available counterparts was investigated by FTIR spectroscopy. Migration of photoinitiators was investigated using a Soxhlet extraction procedure. The amount of extractable photoinitiator and cleavage products was evaluated by elemental analysis. In a second approach, a low migratable photoinitiator with a vii polymerizable group was used in the UV-curing of NR latex via thiol-ene reaction. Mechanical properties of the cured samples and migration behaviour of the photoinitiator were compared with the samples prepared with the parent initiator.

M3 - Doctoral Thesis

ER -