Fluoro acrylic polymers and copolymers: Surface properties and thermal behaviour
1989; Elsevier BV; Volume: 45; Issue: 1 Linguagem: Inglês
10.1016/s0022-1139(00)84576-5
ISSN1873-3328
AutoresClaude Guéry, T. Hugues, N. Kotea, Michel Viguier, A. Commeyras,
Tópico(s)Surface Modification and Superhydrophobicity
ResumoThe wetting properties and thermal behaviour of a series of polyacrylates containing pendant perfluoroalkyl groups RF-CnF2n+1 where n is 4, 6 and 8, have been studied. Polymerisation of fluoro acrylic monomers CH2C(CH3)COO-RH-RF (RH is a non fluorinated spacer RHCH2CH2, CH2-CH(OH)-CH2-, CH2-CH = CH-) and copolymerisation with methacrylic esters (methyl, butyl....) are carried out in solution or emulsion with azo compounds as radical initiators. Reactivity ratios implied a random distribution of fluoro acrylic units in the copolymer chains. Surface tensions (γc and γs) of copolymers are discussed in relation to the composition and the nature of the fluorinated monomer and comonomer. The wettability of copolymers is markedly decreased by the presence of few percents of fluoro monomer and by the length of the fluoroalkyl side chain from n-4 to n-8. The result presented here support the view that the concentration of fluoroalkyl groups is higher at the interface solid/air than in the bulk, the packing of these fluoro groups control the wettability of the surface. The association and arrangement of fluoroalkyl groups are confirmed by DSC studies. Homopolymers with RF C8F17 presented an endothermic peak around 80°C, at this temperature we observed the desappearance of optical birefringence (exothermic peak of cristallisation is observed on cooling). We assumed that this first-order transition corresponds to the melting of fluoro side chains. Melting temperatures and enthalpies are modified by the thermal history of the polymer (quenching, annealing) and their chemical structure. A second transition, with a longer relaxation time is observed, around 60°C.
Referência(s)