Surface morphology and property of UV-cured film containing photopolymerizable polysiloxane-based nanogels with initiating capability

International Journal of Industrial Chemistry (2019) 10:281–289 https://doi.org/10.1007/s40090-019-00193-x RESEARCH Surface morphology and property of UV‑cured film containing photopolymerizable polysiloxane‑based nanogels with initiating capability Meng Wei1,2 · Jun‑yi Han1,2 · Yan‑jing Gao2 · Sheng‑ling Jiang3 · Fang Sun1,2 Received: 23 December 2018 / Accepted: 8 August 2019 / Published online: 17 August 2019 © The Author(s) 2019 Abstract We have synthesized a kind of photopolymerizable polysiloxane-based nanogel with intramolecular-initiating capability based on 4-hydroxybenzophenone (HBP), isobornyl methacrylate (IBMA), urethane dimethacrylate (UDMA) and 2-isocyanatoethyl methacrylate (IEM) and methacrylate-modified polysiloxane (PSMA). The nanogel possesses low migration of photolysis fragments and can dramatically reduce the volumetric shrinkage. In this work, the influences of the nanogels on the properties of UV-cured films prepared with nanogel and triethylene glycol dimethacrylate (TEGDMA) including rheology, glass transition temperature (Tg), tensile property, thermostability, surface morphology and surface energy of the UV-cured films were systematically studied. The results show that with the addition of nanogels at different loading levels, the viscosity increased fast and reached up to 9600 mPa s. The increasing the content of nanogels in formulations resulted in the enhancement of thermal stability and elongation at break of the UV-cured films, and the formation of a more homogeneous network. Moreover, by adding the nanogels, the tensile strength of the cured films and surface energy declined. The enrichment of the nanogel on the surface can generate a more hydrophobic surface. Thus, the nanogels have potentially practical value in tuning structure and properties of polymer networks. Graphic abstract The polymerizable nanogels, which can initiate photopolymerization and reduce volumetric shrinkage, have the remarkable capability in decreasing surface energy, enhancing thermal stability and elongation at break, and homogenizing structure of polymer networks. Keywords Nanogel · Photopolymerization · Mechanical property · Tenacity Electronic supplementary material The online version of this article (https://doi.org/10.1007/s40090-019-00193-x) contains supplementary material, which is available to authorized users. * Fang Sun Extended author information available on the last page of the article Introduction Photopolymer materials, which have a great number of advantages: a wide applied range, high sensitivity, selfprocessing nature and relatively low cost, can be used in 13 Vol.:(0123456789) 282 International Journal of Industrial Chemistry (2019) 10:281–289 biomaterials [1], coatings [2], adhesives [3], printing inks [4], dental materials [5], holographic data storage [6], diffractive and refractive optical elements [7], solar concentrators [8], holographic interferometry and holographic sensors [9]. However, the photopolymer materials usually suffer from high volumetric shrinkage. In the polymerization process, the volumetric shrinkage occurs during crosslinking of the polymeric system and depends on the chemical composition and polymerization reaction. Previously, it was reported that various strategies are applied to reduce the volumetric shrinkage, involving the use of nanoparticle–photopolymer composites [10], liquid crystalline monomers [11], radical/cationic hybrid initiating systems [12], thiol–ene cross-linked systems [13], and nanogels [14]. Nanogels, formed by physically or chemically crosslinked polymer networks with nanoscale size, have been widely researched in the fields of tissue engineering [15], photonic materials [16], drug delivery [17], dental materials [18], modifiers for coatings and polymer composites [19]. In previous research, we reported various reactive nanogels that have shown the capability to reduce the shrinkage stress without significant influences on the mechanical properties of materials [20]. Recently, we have synthesized a series of nanogels with intramolecular-initiating capability for free radical photopolymerization and researched the photochemical properties and photoinitiation mechanism of the nanogels possessing both chromophoric groups and hydrogen donating sites [21]. However, we do not know yet how the nanogels affect the mechanical properties of UV-cured films. It is very important to develop the application of the nanogels. Therefore, dispersing nanogels with different loading levels into dimethacrylate monomer and then various properties of the formulations, including rheology, glass transition temperature (T g), tensile properties and thermostability were evaluated. More importantly, the surface property, morphology and elemental composition of the polymers containing the nanogels also were investigated. Experimental Materials Dual-end terminated methacrylate-modified polysiloxane (PSMA, Mn = 380) was donated by Shin-Etsu Chemical Co. Ltd (Shanghai, China). Isobornyl methacrylate (IBMA) and triethylene glycol dimethacrylate (TEGDMA) were donated by Eternal Chemical Co. Ltd (Zhuhai, China). Diethyl thioether, urethane dimethacrylate (UDMA) and 2-isocyanatoethyl methacrylate (IEM) were purchased from Heowns Business License Co. Ltd (Tianjin, China). 13 2-Mercaptoethanol (ME) was supplied by Fuchen Chemical Reagents Factory (Tianjin, China). Isophorone diisocyanate (IPDI) was obtained from Qingdao Xinyutian Chemical Co. (Qingdao, China). Benzophenone (BP) and 4-hydroxybenzophenone (HBP) were purchased from Sinopharm Group Chemical Reagent Co. (Beijing, China). Azobisisobutyronitrile (AIBN) was purchased from Xilong Chemical Co. Ltd (Shantou, China). Triethanolamine (TEOA) and dibutyltindilaurate (DBTDL) were supplied by Shanghai Chemical Reagents Co. (Shanghai, China). Triethylamine (TEA), ethanol, ethyl acetate, hexane, acetonitrile, phosphorus pentoxide ( P2O5) and dichloromethane (DCM) were purchased from Beijing Chemical Works (Beijing, China). Dichloromethane (DCM) was dried using P 2O5. The nanogels which are designated as Si-HBP10, Si-HBP20, SiHBP30, Si-HBP40 and Si-HBP50, respectively, to represent the 10, 20, 30, 40 and 50 mol% component of HBP in the terminal groups of the nanogel were synthesized by a known procedure [21]. (See Scheme S1). Characterization Transmission electron microscopy (TEM) images were obtained by JEOL JEM-2010 high-resolution transmission electron microscopes. The accelerating voltage was 20.0 kV. The average size and size distribution of the nanogel were measured by dynamic light scattering (DLS) using a Zetasizer NanoZS (ZEN 3600, Malvern, Germany). All measurements were carried out three times in 0.01 w/v % dichloromethane solutions at 25 °C using a 633 nm wavelength beam at 90° scattering angle. Dichloromethane diluting each dispersion was ultrafiltered through a 0.20-μm membrane to remove dust. The tensile properties of UV-cured films were measured by us (...truncated)