Polymer brushes methyl methacrylate

Poly(methyl methacrylate) with a variable degree of polymerization anchored to silica surfaces was synthesized following the room temperature ATRP polymerization scheme described earlier [45,46]. In the main part of Fig. 25 we plot the variation of the PMMA brush thickness after drying (measured by SE) as a function of the position on the substrate. Thickness increases continuously from one end of the substrate to the other. Since the density of polymerization initiators is (estimated to be 0.5 chains/nm ) uniform on the substrate, we ascribe the observed change in thickness to different lengths of polymer chains grown at various positions. 

First experiments which focused on the variation of the conformational properties have been performed by Brown et al. [240], who studied the role of the interactions between matrix and brush polymers (enthalpy driven brush swelling, see Eq. 59). They used a series of polystyrene (PS)-poly(methyl methacrylate) (PMMA) symmetric diblock copolymers with different blocks labeled by deuterium, placed at the interface between PMMA and poly(2,6-dimethylphenylene oxide) (PPO) homopolymers. A double brush layer was created with PMMA blocks dangling into (neutral) PMMA homopolymer and PS blocks immersed in favorably interacting PPO melt (x=Xps/ppo<0)- The SIMS profiles obtained showed that the PS side of the block copolymer is stretched by at least a factor of 2 with respect to the PMMA side. 

Ramakrishnan A, Dhamodharan R, Ruhe J. Growth of poly(methyl methacrylate) brushes on silicon surfaces by atom transfer radical polymerization. J Polym Sci Pol Chem 2006 44 (5) 1758-69. 

We have stndied the macroscopic frictional properties of high-density polymer brushes prepared by surface-initialed ATRP of methyl methacrylate (MM A) [31] and hydrophilic methacrylates [32, 33] from silicon substrates. Friction tests were carried out using a stainless steel or glass ball as the sliding probe under a normal load of 100 MPa from the viewpoint of practical engineering applications. This chapter reviews the macroscopic frictional properties of polymer brushes under a high normal load, the dependence of solvent qnaUty, the effect of humidity on hydrophilic brnsh, and wear resistance, and we compare these with alkylsilane monolayers. 

An alternative (and perhaps more efficient) polymeric surfactant is the am-phipathic graft copolymer consisting of a polymeric backbone B (polystyrene or poly(methyl methacrylate)) and several A chains ( teeth ) such as poly(ethylene oxide). The graft copolymer is referred to as a comb stabiliser - the polymer forms a brush at the solid/liquid interface. The copolymer is usually prepared by grafting a macromonomer such as methoxy poly(ethylene oxide) methacrylate with poly(methyl methacrylate). In most cases, some poly(methacrylic acid) is incorporated with the poly(methyl methacrylate) backbone - this leads to reduction of the glass transition of the backbone, making the chain more flexible for adsorption at the solid/liquid interface. Typical commercially available graft copolymers are Atlox 4913 and Hypermer CG-6 supplied by ICI. 

Yu et al. (2007) developed a phase separation technique to move the CdS nanoparticles reversibly in the perpendicular direction. The CdS nanoparticles were chemically bonded to polystyrene-b-(poly(methyl methacrylate)-co-poly(-methacrylic acid) (CdS)) (PS-b-(PMMA-co-PMAA(CdS))) brushes and could be vertically lowered into the brush by exposure to toluene, whereas they were lifted out of the brush by exposure to acetone (or ethanol). Hence, authors show the possible extension of movement by manipulating the thickness of two blocks of the polymer brushes. 

Markedly, surface-initiated ATRP provides the opportunity to use a variety of functional monomers, to tailor the composition and thickness of the brushes, and to prepare multiple functional surfaces. For example, Zhang et al. prepared poly(methyl methacrylate) (PMMA), poly(acrylamide) (PAAM), and their diblock copolymer (PMMA/PAAM) on the surface of PET film by surface-initiated ATRP [59]. The results indicated that the surface properties of PET film were greatly improved by grafted polymer, the surface of PET film modified by PAAM was hydrophilic, and the surface of PET film modified by diblock copolymer was amphiphilic. This kind of modified PET film may be applied as biocompatible materials, amphiphilic functional film, or conductive film. 

Some polymers are linear, a long chain of connected monomers. PE, PVC, Nylon 66, and poly(methyl methacrylate) are some linear commercial examples found in this book. Branched polymers can be visualized as a linear polymer with side chains of the same polymer attached to the main chain. While the branches may in turn be branched, they do not connect to another polymer chain. The ends of the branches are not connected to anything. Special types of branched polymers include star polymers, comb polymers, brush polymers, dendronized polymers [1], ladders, and dendrimers. A cross-linked polymer, sometimes called network polymer, is one in which different chains are connected. Essentially the branches are connected to different polymer chains on the ends. These three polymer structures are shown in Fig. 3.3. 

---