Fluorinated Side Groups

Two other families of polymers with fluorinated side groups have been investigated in the field of elastomers polysiloxanes and polyphosphazenes [394, 395]. These latter macromolecules, called NPF, have been obtained by chemical change of poly(dichlorophosphazene) as for classic phosphazenes ... 

These a,co-dithiol polymers have been used for the initiation of methacrylates with fluorinated side groups such as... 

In contrast to that, the short fluorinated side groups of poly-XIII did not lead to thermotropic LC phases, but resulted in microphase-separated block copolymers caused by the hydrophobic and oleophobic character of fluorinated polymers. This interpretation was supported by DSC data, which gave the thermal transitions for both blocks. 

It is noteworthy that the formation of a mesophase was sustained in the copolymers even incorporating low proportions of mesogenic fluorinated side groups. Moreover, the introduction of repeat co-units with hexyl substituents lowered Tg by internal plasticization and resulted in a somewhat broader mesophase range for the copolymers relative to the fluorinated homopoymer (e.g. T -Tg = 164°C for copolymer). 

All the polymers that contain fluorine side groups in the molecular structure have excellent high-temperature stability and chemical resistance. Polytetrafluoroethy-... 

Many research groups have been systematically studied the effect of the structure-property relationship on gas transport properties of fluorinated polyimides. In this connection, Kim et al. investigated the effect of incorporating fluorinated alkyl side groups into polyimide membranes in terms of their physical and gas permeation properties (Table 3.5) [61]. They demonstrated four polyimides with fluorinated side groups and another four without side groups by polycondensation of 2-(perfluorohexyl)ethyl-3,5-diamino benzoate (PFDAB) and m-PDA with four aromatic dianhydrides (6FDA, ODPA, BTDA, and PMDA), respectively (Scheme 3.12). 

The investigation revealed that the incorporation of fluorinated side groups into polyimide membranes decreased their surface free energies (TgS), increased solubility parameters and FFVs, and therefore substantially enhanced gas permeability for CO2, O2, N2, and CH4 gases with reduced selectivity for CO2-CH4,02-N2, and CO2-N2 gas pairs depending on the structure of the dianhydride monomers. 

Scheme 3.12 Schematic representation of polyimides with or without fluorinated side groups [61],...

Luo et al. [6] used a polydimethylsiloxane macro-initiator to initiate polymerization of methacrylate monomers with fluorinated side groups to prepare fluorosilicone polymers. To obtain diblock copolymers with a low surface energy, they designed poly(dimethylsiloxane)-block-poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) (PDMS-1 -PHFBMA) diblock copolymers by atom transfer radical polymerization (ATRP) technique. To initiate 2,2,3,3,4,4, 4-heptafluorobutyl methacrylate polymerization, bromine end-capped polydimethylsiloxane (PDMS-Br) was used as the macro-initiator. Scheme 6.5 shows a schematic representation of the PDMS-fc-PHFBMA diblock copolymers. The system was strictly deoxygenated... 

To prepare fluorosilicone polymers, Luo et al. [7] again used a polydimethylsiloxane macro-initiator to initiate polymerization of methacrylate monomers with fluorinated side groups. A poly(dimethy lsiloxane)-block-poly(methylmethacrylate)-block-... 

C. Tang, W. Liu, S. Ma, Z. Wang, C. Hu, Synthesis of UV-curable polysiloxanes containing methacryloxy/fluorinated side groups and the performances of their cured composite coatings. Prog. Org. Coat. 69 (4) (2010) 359-365. 

Fluormated poly(organophosphazenes) have distinctly different properties from their nonfluorinated counterparts. This is due to the stabilizing effect of the fluorinated side groups on the backbone, the hydrophobicity or super-hydrophobicity of films or fibers, and the general biomedical stability and compatibility of polymers with fluorocarbon units in the side group structure. The following examples illustrate some of the main properties. 

Poly(siloxanes)-Based Copolymers With Fluorinated Side Groups A decrease in polymer-polymer interactions was also investigated synthesizing methyl-propenoxyperfluoroalkyl siloxane homopolymers (see Figure 13.14) [28]. For a... 

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