Organic-inorganic Hybrid materials “molecular level mixing” Hard, tough, chemically stable, durable, easy toprocess Sol-gel process generally refers the hydrolysis and polycondensation of alkoxide precursors followed by aging and drying. Hybrid materials containing silica Hybrid materials containing titania Better optical and balanced physical properties

In this study, UV curable hybrid coatings with nano-titania were prepared by the in situ method. Triarylsulfonium salt which produces super reactive free radicals and protonic acid as exposed to UV irradiation has been used for simultaneous in situ construction of organic crosslinking network and nano-titania hybrid films. The formation and morphology of the titania particles could be controlled by extending pre-exposure to moisture and retarding the free radical photopolymerization of acrylates.

Materials Tetrabutyl titanate ( TBT, 99% from Aldrich) Epoxy acrylate resin (EB600, from UCB) Hydroxyethyl methacrylate (HEMA, from Mitsubishi chemical corporation) Triarylsulfonium hexafluoroantimonate mixture (Uvacure 1592, U1592, from UCB) 1-Hydroxy-cyclohexyl –phenyl-ketone (Irgacure184, Ir184, from Ciba) Diphenyl(2,4,6 trimethylbenzoyl)phosphine oxide (Runtecure 1108, TPO, from Runtec Co. Ltd.) 2,2,6,6-Tetramethyl piperidine oxide (TEMPO) was recrystallized after obtained from Acros Chemical Corporation.

2.1 Preparation of the hybrids Figure 2-1 Schematic diagram for the humid cabinet and PET cell A. Instant UV-irradiation as soon as the wet film was placed into the humid cabinet. B. Exposure to moisture in humid cabinet for 90min after UV-irradiation. C. UV-irradiation after the wet film exposed to moisture in the cabinet for a controlled period (5, 15, 30 min, respectively) Method A is default for the preparation of cured hybrid film unless otherwise specified.

* Oraganic component was composed of epoxy acrylate, monomer, photoinitiator and Tween-80.The weight ratio resin(EB600) /monomer(HEMA) =6/4; Tween-80: 0.5% in wt Table 2-1 Compositions of raw material sample Organic component* TBT wt% Processing method U1592 wt% TPO wt% Ir184 wt% TEMPO wt% S5T1-TBT30-A  30A(UV for 2min) S5T1-TEM0.3-TBT30-A  0.330A(UV for 4min) S5T1-TEM0.6-TBT30-A  0.630A(UV for 10min) S5-TBT30-A65.0  30A(UV for 6min) S5-TBT30-C55.0  30C(moisturized for 5min and UV for 6 min) S5-TBT30-C155.0  30C(moisturized for 15min and UV for 6 min) S5-TBT30-C305.0  30C(moisturized for 30min and UV for 6 min) S5-TBT30-B905.0  30B(UV for 6 min and moisturized for 90min) S5-TBT10-A65.0  10A(UV for 6min) S5-TBT20-A65.0  20A(UV for 6min) S5-TBT40-A65.0  40A(UV for 6min) S3-TBT30-A173.0  30A(UV for 17min) S7-TBT30-A87.0  30A(UV for 8min) Ir184-3-TBT30-A7  3.0  30A(UV for 7min)

2.2 Results and discussion

2.2.1 Synthesis of the in-situ cured hybrid films Scheme 2-1 Photogeneration of free radical and super protonic acid from triarylsulfonium salt under UV irradiation Scheme 2-2 Dual effect of triarylsulfonium salt for TBT hydrolysis and acrylates polymerization

Figure 2-1 FT-IR spectra for S5-TBT30 hybrid sample during UV irradiation (a)1700~1600 cm-1 and (b) 1250~400 cm Synthesis of the in-situ cured hybrid films

2.2.2 Morphology of the in-situ cured hybrid films Figure 2-2 SEM micrographs of hybrid films ： (a) S5T1-TBT30-A2;(b) S5T1-TEM0.3-TBT30-A4; (c) S5T1-TEM0.6-TBT30-A10

2.2.2 Morphology of the in-situ cured hybrid films Figure 2-3 SEM micrographs of hybrid films ： (d) S5-TBT30-A6;(e) S5-TBT30-C5 (UV for 6min); (f) S5-TBT30-C15(UV for 6min);(g) S5-TBT30-C30(UV for 6min)

2.2.3 XPS analysis of the in-situ cured hybrid films Figure 2-4 XPS spectra of Ti 2p (a) in the hybrid cured films prepared by different method Reported BE of Ti 2p for TiO 2 : eV

2.2.4 DMA analysis of the in-situ cured hybrid films Figure 2-5 DMA scanning for the hybrid films with different moisture exposure time before UV-irradiation

2.2.5 Physical properties of the in- situ cured hybrid films Table 2-2 Physical properties of the hybrid films Sample Gloss (60°) Pencil hardness Impact strength (Kg  cm 2 ) Flexibility (mm) Pure organic cured film109.52H505 S5T1-TBT H505 S5T1-TEM0.3-TBT H502 S5T1-TEM0.6-TBT H503 S5-TBT H502 S5-TBT H503 S5-TBT H504 S5-TBT30-C587.15H503 S5-TBT30-C H502 S5-TBT30-C H502 S5-TBT30-B105.45H503

Figure 2-6 Photograph of the UV-cured hybrid film The cured hybrid film was transparent with slight yellow.

2.3 Conclusion Triarylsulfonium salt, was used for trigging free radical polymerization of acrylates and producing super protonic acid to drive TBT into titania nano-particle. Titania based hybrid films were prepared by the controlled dual photoreactions and a in-situ sol-gel reaction. The formation and morphology of the titania particles could be controlled by extending pre- exposure to moisture and braking the free radical photopolymerization of acrylates.

2.3 Conclusion XPS analysis indicated that moisture pre-exposure was favorable for improving the titania content in the surface layer of UV-cured film. Physical properties tests showed that the hardness and flexibility of the cured hybrid film were simultaneously improved.

衷心感谢杨建文老师、曾 兆华老师与张夏虹师姐不 厌其烦的耐心指导。他们 认真踏实又富于创新精神 的研究态度以及实事求是 的为人精神对我影响甚深； 在我以后的学习、研究与 工作中，我将以他们为榜 样不懈地努力到底！