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Abstract

Surface functionalization is important for modern science, technology as well as human¡¯s daily life. To endow different surfaces with various unique properties, lots of effort has been devoted to develop innovative chemical methods utilized for surface functionalization. Due to the controllability both spatially and temporally, photo-based functionalization is one of the most convenient surface modification methods. This doctoral thesis mainly focuses on photo-induced thiol chemistries for surface functionalization.

In Chapter 1, an introduction is given to describe the recent progress in the field of surface patterning technologies as well as newly developed photo chemistries.

In Chapter 2, a fast (<15 s), initiator-free and versatile surface photopatterning method based on UV-induced thiol-yne click chemistry for creating precise superhydrophobic-superhydrophilic micropatterns is introduced. The method is based on the formation and modification of alkyne-functionalized polymer surfaces with porous structure. This alkyne surface can be modified with variety of thiol-containing chemicals under UV irradiation without any photoinitiator, in different solvents and even in water rapidly. Superhydrophobic-superhydrophilic micropatterns with feature resolution down to 10 ¦Ìm could be created facilely on this polymer surface. Applications for the formation of microarrays of droplets as well as high-density microarrays of cells are also shown in the chapter.

In Chapter 3, a simple, rapid and convenient surface functionalization method based on UV-induced thiol-ene click chemistry to create transparent and mechanically robust micropatterns on smooth glass or flexible polymer films is described. These patterns enable the fabrication of high-density arrays of low surface tension liquid microdroplets via discontinuous dewetting. A wide range of organic solvents including ethanol, acetone, DMF, dichloromethane and even hexane (surface tension 18.4 mN/m), could be used to produce such microdroplet arrays with complex shapes. This unique method provides an important solution for ultra high-throughput chemical screening applications. The possibility of parallel addition of different chemicals into the individual organic microdroplets is demonstrated. This approach is also employed to create high-density arrays of polymer microlenses with defined 3D shapes. In addition, this method is uniquely suited to create patterns of hydrophobic nanoparticles that can be only dispersed in organic solvents.

In Chapter 4, a UV-induced 1,3-dipolar nucleophilic addition of tetrazoles to thiols is demonstrated. Under UV irradiation the reaction proceeds rapidly at room temperature, with high yields, without a catalyst, and in both polar protic and aprotic solvents, including water. This UV-induced tetrazole-thiol reaction was successfully applied for the synthesis of small molecules, protein modification, and rapid and facile polymer--polymer conjugation. The reaction has also been demonstrated for the formation of micropatterns by site-selective surface functionalization. Superhydrophobic--hydrophilic micropatterns were successfully created by sequential modifications of a tetrazole-functionalized porous polymer surface with hydrophobic and hydrophilic thiols. In addition, a biotin-functionalized surface could be fabricated in aqueous solutions under long-wavelength UV irradiation.

In the last part of this thesis, a brief summarz and outlook are present.