Synthesis And Surface Properties Of Polysiloxane Modified Polyurethane Copolymers

Low surface energy coating polymer because of its unique properties, such as hydrophobicity, non-sticky, and weather resistance, etc., has been widely used in the aviation and aerospace, printing, construction, clothing, and anti-pollution anti-corrosion, etc. With polydimethylsiloxane (PDMS) as soft segment polyurethane (PU) block copolymers by the introduction of low surface energy siloxane structural units, giving a copolymer of low surface energy properties, while polyurethane structural unit also gives excellent mechanical properties of copolymer and surface adhesion. In recent years, polydimethylsiloxane (PDMS) as the soft segment of polyurethane block copolymers has become one of the most active research areas.The relationship between structure and properties of polymer is eternal topic of this area. According to the existing form of PDMS, PDMS-PU copolymer can be divided into two types: segmented and grafted copolymers. The chemical structure, composition and linkage form are the key factors impacting the low surface energy of copolymers. This thesis concerned on the segmented/grafted copolymers, low surface energy, microphase separation and surface chemical composition have been studied to elaborate the relationship of the above three, with a view of providing the basis for molecular design of the polysiloxane modified polyurethane coating low surface energy polymer.With the use of self-polysiloxane soft segment, poly caprolactone (PCL) as mixed soft segments, isophorone diisocyanate (IPDI) as hard segment, aminopropyl triethoxysilane as a chain extender, using two-step solution polymerization, a series of different composition, different ways linked PDMS-PU copolymer. The use of static contact angle, dynamic contact angle study of hydrophobic properties of the copolymer film; using tapping mode atomic force microscope (AFM) study of the copolymer film on the surface to investigate the separation behavior; and using X-ray photoelectron spectroscopy (XPS) analysis of the copolymer membrane surface elements. Explore the surface morphology of phase separation, surface hydrophobic properties, as well as block the relationship between chain structures. 1. synthesis and characterization of different forms of hydroxyl-terminated alkyl polysiloxaneA. With the use of acid treated bentonite as the catalyst, a series of functional polysiloxane hompolymers with relatively narrow molecular weight distribution were successfully prepared.B. A series of mono-functional polysiloxanes with different molecular weight were synthesized. Reaction route for the anionic ring-opening polymerization of D3/F3 was designed and correspondent reactors for the polymerization were constructed.C. Di-Si-H terminal PDMS, mono-Si-H terminal PDMS and mono-Si-H PMTFPS were successfully synthesized, the molecular weight distribution were between 1.2 and 1.4, the repeat unit number were 15,35 and 50, respectively.D. For the use of hexamethyldisilazane as a hydroxyl protecting agent to replace the traditional trimethylchlorosilane hydroxyl protection methods, not only effectively prevent the silicon hydride groups with hydroxyl side-effects between, but also simplify the reaction process to achieve a response to green. Hydrosilylation synthesized double-ended hydroxyalkyl of PDMS, single-ended double-hydroxyalkyl of PDMS, as well as single-ended double-hydroxyalkyl PMTFPS.2. Surface properties of PDMS-PU segmented copolymersA. PDMS can effectively reduce surface energy of copolymer film. Copolymer membrane surface of the water contact angle increases with the PDMS content increased gradually tends to a maximum of about 110°. PDMS chain segments longer; the above phenomenon is more significant. Annealing temperature, the water contact angle is even greater, is conducive to polysiloxane chains on the surface enrichment.B. Advancing contact angle and receding contact angle increases with increasing PDMS content, contact angle hysteresis increases with the PDMS chain segments smaller reduction in the surface of hydrophilic groups are conducive to the formation of a durable low surface energy.C. All the copolymer membrane surface can be observed in 5-20nm scale, micro-phase separation structure. With the PDMS chain segment length, PDMS content increased, the micro-phase separation is significantly enhanced, micro-phase structure "double-continuous phase" to "island" structural changes. High annealing temperature is conducive to polysiloxane chains to the surface enrichment, micro-level phase separation increased, relative to district size increases.D. Elements in the coating the surface of silicon noticeable enrichment of siloxane chain segments extending toward the air interface, the changes in silicon with depth gradually decreased, when the information depth of about 10nm when the elements are still larger than the bulk composition, PDMS chain segments increased, PDMS content increased and the annealing temperature are conducive to the surface of silicon enrichment.3. Surface properties of PDMS-PU grafted copolymerA. PDMS (PMTFPS) can effectively reduce the surface energy of copolymer film. Copolymer membrane surface of the water contact angle with the increase of polysiloxane content increased gradually tends to a maximum of about 110°. In this study, within the polysiloxane composition, water contact angle and the polysiloxane chain length has little to do. Annealing temperature, the water contact angle is even greater, is conducive to polysiloxane chains on the surface enrichment.B. Advancing contact angle and receding contact angle increases with increasing PDMS content, contact angle hysteresis increases with the PDMS chain segments smaller reduction in the surface of hydrophilic groups are conducive to the formation of a durable low surface energy.C. In this article, within the scope of the study, grafted copolymer membrane surface can not form a clear micro-phase separation of nano-size, surface enrichment layer of uniform polysiloxane.D. Elements in the coating the surface of silicon noticeable enrichment of siloxane chain segments extending toward the air interface, the changes in silicon with depth gradually decreased, when the information depth of about 10nm when the elements are still larger than the bulk composition, PDMS chain segments increased, PDMS content increased and the annealing temperature are conducive to the surface of silicon enrichment.E. The introduction of fluorinated groups little effect on their surface properties. 4. The influence of surface properties, surface morphologies by linkage formA. Segmented and grafted two kinds of links means links siloxane-modified polyurethane coatings can effectively reduce the surface energy, with the PDMS content increased the surface enrichment of polysiloxane chains tends to a constant, the water contact angle to stabilize The maximum value of about 110°. The static contact angle of grafted copolymers larger than segmented copolymers, while contact angle hysteresis is more evident, showing the surface can be lower, but difficult to maintain a durable low surface energy.B. In the same composition, the segmented copolymer formed a clear link to the surface of micro-phase separation structure, the surface of Si elements is relatively small, hydrophobic groups on the surface enrichment is relatively weak.C. The performance of the surface of grafted copolymers can be lower, but difficult to maintain a durable low surface energy may be related to the nature of the high degree of freedom of polysiloxane chains, chain segment movement ability, and at the same time easy-to-surface Enrichment and surface reconstruction.