Polymer films hyperbranched polymers

NLO effects in the thin films. Hyperbranched polymers should be ideal matrix materials as they offer three-dimensional spatial separation of the NLO chromophores in the spherical architecture, and their void-rich topological structure should help minimize optical loss in the NLO process. 

Fig. 21 —Friction force and topography images of the L-B films of Cgo-Pst hyperbranched polymer under load 2 nN using AFM/FFM, image (a) and (b) are friction force images and image (c) is the topography.

Diagram of friction versus load of multilayer L-B film of Pst hyperbranched polymer molecules (two layers). 

Several applications of hyperbranched polymers as precursors for synthesis of crosslinked materials have been reported [91-97] but systematic studies of crosslinking kinetics, gelation, network formation and network properties are still missing. These studies include application of hyperbranched aliphatic polyesters as hydroxy group containing precursors in alkyd resins by which the hardness of alkyd films was improved [94], Several studies involved the modification of hyperbranched polyesters to introduce polymerizable unsaturated C=C double bonds (maleate or acrylic groups). A crosslinked network was formed by free-radical homopolymerization or copolymerization. 

Keywords. Hyperbranched macromolecules. Polymer films. Scanning force microscopy. Conformational transitions and interfacial ordering of single molecules... 

Fig. 13a,b. a Surface pressure - film area isotherms of (1) dendrimer 1, (2) dendrimer 2, and (3) hyperbranched polymer with OH end groups [74]. b Schematic interpretation of the phase transitions from a dense monolayer (I) via a reoriented monolayer (II) to a thick liquid film (III)... 

Finally, hyperbranched polymer layers by surface-initiated step polymerization was intensively studied mainly by Bergbreiter et al. and Crooks et al. Patterned surfaces were prepared on the micrometer scale and a variety of functional groups introduced interesting optical, electrochemical, biological, and mechanical properties into the films. For a recent review on surface-initiated step polymerization resulting in branched polymer layers see [352]. 

Hong, Y., Coombs, S. J., Cooper-White, J. J., Mackay, M. E., Hawker, C. J., Malmstrom, E., and Rehnberg, N. 2000. Film blowing of linear low density polyethylene blended with a novel hyperbranched polymer processing aid. Polymer, 41, 7705-7713. 

Deposition of a monolayer film of 3S at 20 mN/m surface pressure on a silicon wafer was achieved by z-type with transfer efficiency consistently in the range of about 0.5-0.6 (Figure 2). Such low transfer may imply that the hyperbranched polymer can be squeezed under compression, through either conformational change or intercalation. The overcompression could be relieved by transfer onto a solid substrate where the molecule occupies an area larger than on the water/air interface. The thickness of the deposited monolayer measured by ellipsometry was about 32A for the first few layers, but this number declined slowly as the number of depositions increased. The homogeneity of the film, judged from the standard deviation of the film thickness, also deteriorated. The... 

---