Simulation And Experimental Study On Copper-mediated Atom Transfer Radical Polymerization

ATRP was thought as an extremely powerful synthetic technique due to the broad range of monomers and moderate experimental conditions,as well as the ability for the preparation of numerous well-defined materials with various applications.The success of the method can be attributed to detailed mechanistic studies that paved the way for creating rules for the rational selection of reaction conditions to achieve the synthesis of the desired well-defined functional macromolecules.With the development of ATRP technique,some new methods involved basic ATRP mechanism have emerged,such as SET-LRP/SARA ATRP,photo ATRP and eATRP,which have shown their advantages on functional polymer synthesis.On the other hand,stimulus-responsive materials that responding to light irradiation,temperature,pH,salt and so on,have attracted much attentions because of their protential applications in durg delivery,catalysis,smart surface,etc.Meanwhile,surfaces that with hydrophobicity,and antifouling behaviors can be achieved by using the fluoropolymer based coating.Therefore,preparing new fluorinated materials with both stimulus responsivity and hydrophobicity is very important for the construction of stable smart material.In this work,model-based design and preparation of stimulus-responsive fluorinated polymers and their performances were carried out based on polymer chemistry and engineering methodologies.To be specific,comprehensive kinetic models were first developed for normal ATRP,SARA ATRP and photo ATRP on the basis of their mechanism and reaction engineering knowledge,which can be used to optimize the experimental conditions and get insight into the reaction processes;then,the stimulus responsive fluorinated polymers were designed and prepared for fabricating smart surfaces based on polymer chemistry and material science.The contents of each part are listed as follows:?1?The effect of initiator type?i.e.,micro-molecular,macromolecular and immobilized initiator?on the ATRP kinetics was studied through a developed mathematical model.It was validated thoroughly via experiments using fluorinated monomer[2,2,3,3,4,4,4-heptafluorobutyl methacrylate?HFBMA?]as model component.The results showed that the activity and deactivity for the same catalytic complex was the highest for ethyl 2-bromoisobutyrate?Eib-Br?,lower for bromo-poly?styrene??PS-Br?,and the lowest for bromo-aminopropyl functionalized SiO₂?SiO₂-APTS-Br?.In comparison,the effect of initiator structure on deactivation rate coefficient was greater than that on activation rate coefficient.The increase in k_a helped the improvement of polymerization rate,and the increase in k_da had positive effects on reaction controllability and functionality.Especially,the addition of deactivator in SiO₂-APTS-Br initiation system was beneficial for improving the controllability of polymerization.?2?Novel fluorinated random and gradient copolymers,i.e.poly?HFBMA-r-BIEM-graft-SPMA?and poly?HFBMA-g-BIEM-graft-SPMA?,were designed and prepared via normal ATRP for smart surface with light-responsive controllable wettability and excellent stability.Compared to random copolymer,gradient copolymer showed its advantage in?T_g?=30??.This broader T_g response region should be resulted from its unique composition profile.In addition,the absorbance intensity at solid state decreased obviously and the time required to attain photo-stationary state of spin-coated film was longer than that in solution,which indicated that the limited free volume and restricted conformational freedom of polymer chains in spin-coated film lead to slow down the isomerization of bulky SP units.Thanks to the functional film and surface roughening,?WCAs of etched silicon surfaces fabricated by random copolymer was 19.9°and fabricated by gradient copolymer was 28.8°.?3?A comprehensive kinetic model based on the mechanism of supplemental activator and reducing agent atom transfer radical polymerization?SARA ATRP?was developed to better understand the kinetics of copper?0?-mediated reversible-deactivation radical polymerization[Cu?0?-mediated RDRP].Simulation results showed that diffusional limitation on termination affects polymerization significantly.A comprehensive description of the variation trend of soluble species and reaction rates during polymerization was illustrated by simulation.The effects on kinetics of four key rate constants(i.e.,k_{a 0},k_{dis p},k_{a 1},k_comp)involved in Cu?0?-mediated RDRP showed that faster activation by Cu?0?leaded to the polymerization kinetic behavior deviation from that in living radical polymerization;faster disproportionation of Cu^IX/L could not ensure the reaction to proceed successfully;slower activation by Cu^IX/L could not control the molecular weight and its distribution;the comproportionation of Cu^IIX₂/L and Cu?0?did not predominantly affect the kinetic behavior of polymerization,and an appropriate rate coefficient could control over the molecular weight and its distribution.Finally,Cu?0?-mediated RDRP of methyl methacrylate?MMA?and butyl methacrylate?BMA?were conducted to study the polymerization kinetics.Results showed that the Cu?0?surface area-dependent apparent value followed the relationship of ???in previously published works.Addition of an initial Cu^IIBr₂ deactivator could significantly improve the controllability of polymerization.?4?Three block copolymers with different PAA segment lengths,i.e.PHFBMA₇₀-b-PAA₇₃,PHFBMA₇₀-b-PAA₁₄₈,PHFBMA₇₀-b-PAA₂₁₁,were synthesized through Cu?0?-mediated reversible-deactivation radical polymerization?SARA ATRP?and hydrolysis reaction.pH-induced surface wettability was achieved by spin-coating the resulting block copolymers onto silicon wafers.Results showed that the responsiveness of as-fabricated surfaces was greatly influenced by PAA content.The difference of WCA between acidic condition and basic condition showed a maximum value??WCA?40^o?for the surface coated by PHFBMA₇₀-b-PAA₁₄₈.The other surfaces have similar?WCA of 30^o.Furthermore,a simple solution-casting technique was developed to functionalize the stain steel meshes?SSMs?by using the as-prepared block copolymers to separate layered water/oil mixtures.Given their superhydrophilicity and underwater superoleophobicity,as well as the long-term use,the PHFBMA₇₀-b-PAA₁₄₈ coated SSM with high separation efficiency,high water flux and good stability may be the best copolymer for water/oil separation.?5?A detailed kinetic insight into photochemically mediated atom transfer radical polymerization?photo ATRP?was presented through a validated comprehensive model.The simulation mimics the experimental results of the model system using optimized photochemically mediated radical generation rate coefficients.A comprehensive description of the variation trend of soluble species and reaction rates during polymerization was illustrated by simulation.The effect of the reaction parameters on ATRP behaviors was also investigated.Results showed that the reduction of induction period was achieved by increasing the overall photochemically mediated radical generation rate coefficients?k_r?,the free ligand concentration,and the initiator concentration;the acceleration of polymerization rate followed the square root law in the above three cases.However,the induction period reduced by decreasing the catalyst concentration,and the independence of the apparent propagation rate coefficient(k_p^app)on the square root of catalyst concentration might be attributed to the result of the synergy between the activators regenerated by electron-transfer?ARGET?ATRP and the initiators for continuous activator regeneration?ICAR?ATRP mechanism.?6?A well-defined functional material poly?2,2,3,4,4,4-hexafluorobutyl methacrylate?-block-poly?N-isopropylacrylamide??PHFBMA-b-PNIPAAm?was synthesized through a new environmentally benign?living?radical polymerization technique[i.e.photo-initiated atom transfer radical polymerization?photo ATRP?].The synthesized functional copolymer was considered as a modifier for fabricating a smart surface with thermal-responsive wettability.Results showed that the as-frabricated surface can reversibly switch between hydrophilicity?WCA=50°?and hydrophobicity?WCA=104°?,which results from the synergistic effect of surface chemical composition,reorientation of functional groups,and roughness in response to temperature.Finally,a smart separation device was constructed and used for separating water/oil mixture with high penetration flux(2.50 L s^-1 m^-2 for water removing,2.78 L s^-1 m^-2 for oil removing)and well efficiency?>98%?.