title: Thermoreversible gelation of poly(vinylidene fluoride) in phthalates: the influence of aliphatic chain length of solvents.
abstract: Thermoreversible gelation of poly(vinylidene fluoride) (PVDF) has been studied in a new series of solvents (phthalates), for example, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), and dihexyl phthalate (DHP) as a function of temperature and polymer concentration, both by test tube tilting and dynamic light scattering (DLS) method. The effect of aliphatic chain length (n) of diesters on the gelation kinetics, structure/microstructure and morphology of PVDF gels has been examined. Gelation rate was found to increase with increasing aliphatic chain length of diester. DLS results indicate that the sol-gel transformation proceeds via two-steps: first, microgel domains were formed, and then the infinite three-dimensional (3D) network is established by connecting microgels through polymer chains. The crystallites are responsible for 3D network for gelation in phthalates, and alpha-polymorph is formed during gelation producing higher amount of crystallinity with increasing aliphatic chain length of diester. Morphology of the networks of dried gels in different phthalates showed that fibril thickness and lateral dimensions decrease with higher homologues of phthalates. The scattering intensity is fitted with Debye-Bueche model in small-angle neutron scattering and suggested that both the correlation length and interlamellar spacing increases with n. A model has been proposed, based on electronic structure calculations, to explain the conformation of PVDF chain in presence of various phthalates and their complexes, which offer the cause of higher gelation rate for longer aliphatic chain length.
authors: School of Materials Science and Technology, Institute of Technology, Department of Chemistry, Banaras Hindu University, Varanasi 221 005, India.
authors: P Jaya Prakash
authors: PJ
authors: Yadav
authors: Goutam
authors: G
authors: Ghosh
authors: Biswajit
authors: B
authors: Maiti
authors: Vinod K
authors: VK
authors: Aswal
authors: P S
authors: PS
authors: Goyal
authors: Pralay
authors: P
authors: Maiti
mesh_terms: D003993:Dibutyl Phthalate / Q000737:chemistry*; D005782:Gels; D008958:Models, Molecular; D015394:Molecular Structure; D010316:Particle Size; D010795:Phthalic Acids / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011145:Polyvinyls / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014753:Vinyl Compounds / Q000737:chemistry*; D005465:Fluorocarbon Polymers
chemical_list: D003993:Dibutyl Phthalate; D005782:Gels; D010795:Phthalic Acids; D011108:Polymers; D011145:Polyvinyls; D014753:Vinyl Compounds; C024629:dimethyl phthalate; C024865:polyvinylidene fluoride; D005465:Fluorocarbon Polymers; C007384:1,1-difluoroethylene; C027387:di-n-hexyl phthalate; C007379:diethyl phthalate