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1.
ACS Omega ; 5(25): 15192-15201, 2020 Jun 30.
Article in English | MEDLINE | ID: mdl-32637792

ABSTRACT

Photoinduced thiol-epoxy click polymerization possesses both the characteristics and advantages of photopolymerization and click reactions. However, the photopolymerization of pigmented or highly filled thiol-epoxy thick composites still remains a great challenge due to the light screening effect derived from the competitive absorption, reflection, and scattering of the pigments or functional fillers. In this article, we present a simple and versatile strategy to prepare thick composites via delayed thiol-epoxy photopolymerization. The irradiation of a small area with a light-emitting diode (LED) point light source at room temperature leads to the decomposition of a photobase generator and the released active basic species can uniformly disperse throughout the whole system, including unirradiated areas, via mechanical stirring. No polymerization was observed at room temperature and therefore the liquid formulations can be further processed with molds of arbitrary size and desired shapes. It is only by increasing the temperature that base-catalyzed thiol-epoxy polymerization occurs and controllable preparation of thick thiol-epoxy materials can be achieved. The formed networks display excellent uniformity in different radii and depths with comparable functionality conversions, similar T g values, and thermal decomposition temperatures. The presented strategy can be applied to prepare thick composites with glass fibers possessing improved mechanical properties and dark composites containing 2 wt % carbon nanotubes.

2.
Chem Commun (Camb) ; 54(8): 920-923, 2018 Jan 23.
Article in English | MEDLINE | ID: mdl-29318224

ABSTRACT

A bis(acyl)phosphane oxide (BAPO) photoinitiator was conveniently synthesized in an efficient one-pot process. It shows excellent dispersibility in water, good storage stability, and high photo-reactivity in 3D printing of hydrogels under visible-light irradiation (460 nm).

3.
Angew Chem Int Ed Engl ; 57(9): 2353-2356, 2018 02 23.
Article in English | MEDLINE | ID: mdl-29266601

ABSTRACT

Cellulose nanocrystals (CNCs) with >2000 photoactive groups on each can act as highly efficient initiators for radical polymerizations, cross-linkers, as well as covalently embedded nanofillers for nanocomposite hydrogels. This is achieved by a simple and reliable method for surface modification of CNCs with a photoactive bis(acyl)phosphane oxide derivative. Shape-persistent and free-standing 3D structured objects were printed with a mono-functional methacrylate, showing a superior swelling capacity and improved mechanical properties.

4.
Angew Chem Int Ed Engl ; 56(45): 14306-14309, 2017 11 06.
Article in English | MEDLINE | ID: mdl-28857401

ABSTRACT

Star-shaped polymers represent highly desired materials in nanotechnology and life sciences, including biomedical applications (e.g., diagnostic imaging, tissue engineering, and targeted drug delivery). Herein, we report a straightforward synthesis of wavelength-selective multifunctional photoinitiators (PIs) that contain a bisacylphosphane oxide (BAPO) group and an α-hydroxy ketone moiety within one molecule. By using three different wavelengths, these photoactive groups can be selectively addressed and activated, thereby allowing the synthesis of ABC-type miktoarm star polymers through a simple, highly selective, and robust free-radical polymerization method. The photochemistry of these new initiators and the feasibility of this concept were investigated in unprecedented detail by using various spectroscopic techniques.

5.
ACS Appl Mater Interfaces ; 8(30): 19764-71, 2016 Aug 03.
Article in English | MEDLINE | ID: mdl-27403625

ABSTRACT

A simple and straightforward synthesis was developed to prepare the siloxy-substituted bis(acylphosphane)oxide 4-(trimethoxysilyl)butyl-3-[bis(2,4,6-trimethylbenzoyl)phosphinoyl]-2-methyl-propionate TMESI(2)-BAPO. This new photoinitiator was successfully fixed to glass surfaces. Subsequent irradiation with UV light in the presence of either a partially fluorinated acrylate or a specifically synthesized polysiloxane containing polymerizable acrylate functions allowed the generation of polymer chains which grew from the surface in an efficient radical polymerization process ("grafting-from" procedure). Durable hydrophobic surfaces were prepared which have contact angles between 93° and 95°. The silanization process with the photoinitiator and the grafting process were followed and analyzed with various techniques including high-resolution X-ray photoelectron spectroscopy.

6.
Chem Commun (Camb) ; 52(64): 9917-20, 2016 Aug 02.
Article in English | MEDLINE | ID: mdl-27431207

ABSTRACT

Bis(mesitoyl)phosphinic acid and its sodium salt display a unique photo-induced reactivity: both derivatives stepwise release two mesitoyl radicals and, remarkably, metaphosphorous acid (previously postulated as transient species in the gas phase), providing a new phosphorus-based reagent.

7.
Macromol Rapid Commun ; 36(6): 553-7, 2015 Mar.
Article in English | MEDLINE | ID: mdl-25651079

ABSTRACT

The sodium salt of the new bis(mesitoyl)phosphinic acid (BAPO-OH) can be prepared in a very efficient one-pot synthesis. It is well soluble in water and hydrolytically stable for at least several weeks. Remarkably, it acts as an initiating agent for the surfactant-free emulsion polymerization (SFEP) of styrene to yield monodisperse, spherical nanoparticles. Time-resolved electron paramagnetic resonance (TR-EPR) and chemically induced electron polarisation (CIDEP) indicate preliminary mechanistic insights.


Subject(s)
Oxides/chemistry , Phosphines/chemistry , Polymers/chemical synthesis , Surface-Active Agents/chemistry , Emulsions/chemistry , Polymerization , Polymers/chemistry
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