Functional Coating Materials Based On Si-doped Carbonized Polymer Dots As Building Blocks

Coating is a solid continuous protective film formed by polymer resin curing,which can be coated on metal,fabric,wood,plastic and other substrates for purposes include protection,encapsulation,decoration and so forth.The mechanical properties of coating are directly related to its application range,service life and protection effect.Polymer coatings possess the advantages of light weight,strong impact resistance,good flexibility,and accessible processing.However,compared with inorganic coatings（such as SiO₂,ZrO₂,TiO₂,and so forth）,polymer coatings have deficiency include low surface hardness and poor wear resistance.In order to overcome the disadvantages of low polymer hardness and wear resistance,a common method is to introduce inorganic nanoparticles into the polymer substrate.However,due to the different hydrophilicity and hydrophobicity between the polymers matrix and inorganic nanoparticles,as well as the high surface energy of inorganic nanoparticles,it is prone to aggregation in polymer matrix,impairing the mechanical and optical performance of composite material.Moreover,with the appearance and development of the wearable device,flexible display screen and foldable mobile phone in recent year,new requirements have been putting forward for the flexibility,surface wear resistance and light transmittance of protective coatings.The traditional direct hybridizing process for the preparation of organic-inorganic composite materials is hard to satisfy these requirements.Therefore,a new method is necessary to develop for preparation of this kind coating material.Based on the coating microstructure,it should meet:first,there are both presenting of organic and inorganic phases in coating,organic component provides excellent flexibility and inorganic component provides outstanding abrasion resistance for coating;second,in order to preventing the reduction of transmittance cause by light scatter,organic and inorganic phases should be hybridized at the nano-scale;third,there need be strongly bonded between two phases that could keep the homogeneity of coating.According to the above,a homogeneous hybridized transparent flexible coating material with excellent wear resistance was developed in this study.The specific contents are as follows:In chapter 2,we firstly prepared coating resin（Si-CPDs）by hydrothermal method using aminopropyl oligomer siloxane（APOS）and citric acid（CA）as reactants.Si-CPDs consist of special core-shell structure,of which interior is grapheme lattice and exterior is amino and reactive silanol groups.Si-CPDs show good film-forming performance and can be used as protective coating through dehydration of silanol group by thermal curing.Due to organic and inorganic phases are hybridized in nano-scale,the coating shows excellent transparency with above 90%transmittance in visible light scope.It was found that within a certain range,the modulus and hardness of the coatings increased gradually with the increase of CA:APTES molar ratio.The pencil hardness of the coating can reach 9H,and after 4000 times of steel-wool abrasion（load is 14.85 KPa）,the surface is still intact and without observing scratches.At the same time,the coating exhibits excellent flexibility,and its inner bending diameter can reach 5 mm.In chapter 3,in order to further improve the flexibility of the coating,and satisfy the needs of the bending resistance of folding screen mobile phones,we designed and synthesized tetramethyldisiloxane dipropylaminetetraacetic acid（DSTA）,and prepared Si-CPDs using DSTA and APTES as raw materials.In order to improve the moisture resistance of the coating,3-glycidyloxypropyltrimethoxysilane（GPTMS）was selected to modify the amino groups on the surface of the prepared Si-CPDs by end-capping.The modified Si-CPDs are compouned with hydrophobic polydimethylsiloxane（PDMS）to use as coating resin,and a flexible hard abrasion-resistant coating with good moisture resistance can be prepared by thermal curing.PDMS is enriched on the surface of the coating due to the hydrophilic-hydrophobic interaction,and does not affect the light transmittance of the coating.Because of the introduction of PDMS,the coating obtains a good hydrophobic and anti-fouling effect.The obtained coating show excellent abrasion resistance（without observed scratch after 4000 times steel-wool abrasion test under 14.85KPa load）.Because DSTA has a siloxane structure introduced into the molecular chain,the coating exhibits excellent flexibility,and its inner and outer bending diameters could reach 1 mm.After repeated bent test,the coating shows no crack and peel.In chapter 4,the Si-CPDs coating is modified to endow its hydrophilicity and antifogging function.Firstly,Si-CPDs are prepared using APOS and ethylene diaminetetraacetic acid（EDTA）and APTES as reactants.And then,the coating resin solution is prepared by mixing of ethylene oxide（EO）,GPTMS and Si-CPDs.Epoxy group can react with amino of Si-CPDs.EO is formed hydrophilic site with Si-CPDs.GPTMS is formed cross-linking reaction site with Si-CPDs.The effects of EO:GPTMS ratio on the anti-fog properties and mechanical properties of coatings were investigated.It was found that increasing the amount of EO helps to improve the anti-fog properties of the coating.Increasing the amount of GPTMS helps to improve the mechanical properties of the coating.Finally,when EO:GPTMS=1:1,a hydrophilic anti-fog coating with a surface hardness of 5H and an anti-fog time of 52 seconds was obtained.The coating can be withstood 1000 cycles medical gauze abrasion test under load of 14.85 KPa.