Preparation And Application Of Polymer Films On Silicon Via Surface Initiated Ring-Opening Metathesis Polymerization

Polymer materials have become the necessities of the agricultural, aviation, industrial and daily life. Ring-Opening Metathesis Polymerization (ROMP) has attracted more and more attention due to its characteristics of living polymerization.Polymer films have attracted significant interest because of their applications in nanopattern fabrication, preparation of―smart‖materials and chemical sensing.―Surface grafting‖method has been used to covalently attach polymer films to various substrates. Surface-initiated polymerization can be widely used in the field of modification of the solid material surface. Among different approaches, Surface-Initiated Ring-Opening Metathesis Polymerization (SIROMP) has been researched and applied extensively because of its mild condition, high polymerization rate, and the characteristics of its polymerization. As an effective method to prepare functional polymer films, SIROMP could tether polymer chains effectively to substrates including gold, silicon wafers, steel, and silica nanoparticles.A specialty of ROMP is that the double bond functionality of the monomer is preserved in the backbone of resulting polymer, which allows for further chemical modi(?)cation to yield desired functionalities, such as sulfonate, epoxide and hydroxyl derivatives. The preserved ole(?)ns in SIROMP enable the surface-bound polymers to be easily modi(?)ed. However, SIROMP (?)lms degraded acutely during the process of modi(?)cation of ole(?)n to other functionality. This limits the use of chemical modi(?)cation of SIROMP (?)lms.Current methods to prevent the degradation require inert atmosphere or chemical protection, which limits their applications. The main idea of this paper is the preparation and the application of functional polymer films based on SIROMP method, and a simple method to complete modification of grafted the (?)lms without scission of chains under relatively mild condition.We studied the influence of reaction condition to the ROMP of norbornene from silicon using the first generation Grubbs catalyst, and acquired the best condition to prepare polynorbornene (PNb) films covalently attached on silicon using SIROMP technology. Using SIROMP, we prepared PNb film and polybutadiene films covalently linked on the silicon by polymerizing norbornene and cyclooctadiene in vapor phase. Norbornene derivative monomers with polyethylene glycol (PEG) modified side chains were polymerized from silicon surface. The protein resistance of the PNb-PEG surface was studied. PNb-PEG550 membrane with shorter PEG chains adsorbed less protein than PNb-PEG2000 which PEG chains are longer. Films with larger thickness adsorbed less protein. The PNb-PEG films had better anti-absorption ability to the proteins with large molecular weight.In the present study, covalently tethered PNb (?)lms were prepared via SIROMP from silicon surface, and then epoxidized with meta-chloroperoxybenzoic acid. The interactions between grafted polymers and solvents, which were investigated by characterizing the free counterparts in solution, were found to have a strong impact on the loss of (?)lms. Solvent selection played a major role in the achievement of epoxidation. Here we propose a strategy to achieve complete epoxidation of grafted PNb (?)lms with avoided scission of chains under relatively mild condition just by solvent control. Toward this end, a model of gradient epoxidation has been built by comparing the kinetics results of different depth of the film. The grafted PNb (?)lm was found to be epoxidized gradiently from the surface toward the silicon substrate without scission of chains in the solvents that poorly dissolve PNb while well dissolve the resulting epoxidized PNb.Herein, thermophilic esterase AFEST was employed as catalyst in the polymerization of (?) -caprolactone from the P[Nb(OH)₂] modified silicon in nonaqueous medium. The condition of enzymatic ring-opening polymerization was studied. The length of grafted poly((?) -caprolactone) (PCL) chains could be controlled through the time of enzymatic polymerization, and the surface density of the grafted PCL chains could be controlled through the conversion of the double bonds in the PNb. The PCL content on the surface could be adjusted depending on the need. The stability of the poly( (?) -caprolactone) film was studied: the presence of (?) -caprolactone monomer could stabilize the film in the polymerization system; in order to avoid the degradation of the grafted PCL, it is necessary to separate the film sample from AFEST when the polymerization is finished.