Preparation Of PDMAEMA Polymer Brush And Their Properties

This paper involves two main parts:the optimum preparation method of poly(2-(dimethylamino) ethyl methacrylate)(PDMAEMA) polymer brush via surface initiated atom transfer radical polymerization (SI-ATRP) and the surface stimuli-responsive properties and other surface chemical properties.By optimizing the preparation conditions and researching the reaction kinetics, PDMAEMA polymer brushes with different responsive properties were successfully obtained. The initiator grafting efficiency of one-step is superior to two-step. High temperature play a key role in obtaining smooth initiator self-assembly monolayer. As for the solvent choice of SI-ATRP, solvents, such as ethyl acetate and anisole, make ATRP solution in heterogeneous, and not suitable for operation, while solvents, such as alcohols, DMF, and acetone, can give homogeneous solutions. However, there is an ester exchange reaction between alcohols and DMAEMA monomers and a chain transfer reaction of DMAEMA monomers in DMF, which make them also unsuitable to be used as solvents for ATRP. At last, acetone was chosen as the ATRP solvent due to the homogeneous solutions and higher monomer conversion. The halogen exchange reaction at surface triggers SI-ATRP. Increasing the amount of the catalyst Cu(I) will promote the reaction rate evidently, while adding the deactivator Cu(II) will slow down the ATRP reaction.The thickness of PDMAEMA brush can be controlled by the amount of monomers in the reaction system. We tried three methods to adjust the initiator grafting density on the surface. By mixing synthetic inert initiator and active initiator, the initiator density can not be controlled accurately. By mixing silane coupling agent and active initiator, the initiator density can be well controlled but with heterogenous particles on obtained surfaces. At last, smooth film surfaces with controlled initiator density and low roughness are acquired by controlling initiator concentration at high temperature.The PDMAEMA brushes show pH-responsive properties with contact angle increment of about41°when increasing pH value from3to11. Although it is not so significant temperture-responsive phenomenon is observed (with the contact angle increment of～24°). At pH=1, carboxylate-modified polystyrene microspheres can easily adsorb on the PDMAEMA brushes with positive charges. The PDMAEMA brush shows an obvious resistance to oil pollution in water due to its hydrophilicity.