Abstract
An innovative photopolymerizable microgel modified UV-cured acrylic-silica hybrid formulation was developed and characterized for possible use as protective coating for different substrates. A deep investigation, aiming at providing a strong scientific basis for the production of organic-inorganic (O-I) hybrids exhibiting phase co-continuity, was firstly carried out. The O-I hybrid first proposed in this study was obtained from organic precursors with a high siloxane content, which are mixed with tetraethoxysilane (TEOS) in such a way to produce co-continuous silica nanodomains dispersed within the crosslinked organic phase, as a result of the sol-gel process. The first part of the research deals with the selection and optimization of suitable systems through appropriate chemical modifications, in order to ensure that curing reactions can be carried out at room temperature and in the presence of UV radiation. Firstly, the silica domains are formed, followed by crosslinking reactions of the acrylic groups in the oligomer via a free radical polymerization. The crosslinking reaction was controlled with the use of a suitable photoinitiator. Most of the experimental work was devoted to understanding the morphology of the hybrid system, both in uncured and cured states, and to assess its final thermal and optical properties, using different experiential techniques.
Highlights
In recent years, there has been considerable research interest in a new class of materials, generally known as organic-inorganic (O-I) hybrids
The obtained co-continuous hybrid system is composed of nanosized silica domains, whose presence is assured by the relative easiness with which hydrolysis and condensation reactions can be controlled by an alkoxide precursor, such as TEOS
The polydimethylsiloxane functionalized with MPTS (PDMSm) was added to the alkoxide precursor to obtain an organic-inorganic acrylic-silica network produced by a dual mechanism, i.e., the condensation reaction of the hydrolyzed alkoxy groups and autocatalytic free radical polymerization, respectively
Summary
There has been considerable research interest in a new class of materials, generally known as organic-inorganic (O-I) hybrids. The method combines the sol-gel reaction, involving as the silica precursor tetraethoxysilane (TEOS), with a photopolymerization process The latter technique is becoming increasingly important in the field of coatings [27,28]: it induces the polymer formation with a fast transformation of the liquid monomer into a solid film possessing tailored physical-chemical and mechanical properties. It is considered an environmental friendly technique, due to the solvent-free process, usually carried out at room temperature [27,28,29]. The properties and characteristics of an uncured and a dual-cured hybrid system were deeply analyzed and compared with those displayed by a control organic formulation
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