title: Comparative kinetic study and microwaves non-thermal effects on the formation of poly(amic acid) 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4,4'-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (BAPHF). Reaction activated by microwave, ultrasound and conventional heating.
abstract: Green chemistry is the design of chemical processes that reduce or eliminate negative environmental impacts. The use and production of chemicals involve the reduction of waste products, non-toxic components, and improved efficiency. Green chemistry applies innovative scientific solutions in the use of new reagents, catalysts and non-classical modes of activation such as ultrasounds or microwaves. Kinetic behavior and non-thermal effect of poly(amic acid) synthesized from (6FDA) dianhydride and (BAPHF) diamine in a low microwave absorbing p-dioxane solvent at low temperature of 30, 50, 70 °C were studied, under conventional heating (CH), microwave (MW) and ultrasound irradiation (US). Results show that the polycondensation rate decreases (MW > US > CH) and that the increased rates observed with US and MW are due to decreased activation energies of the Arrhenius equation. Rate constant for a chemical process activated by conventional heating declines proportionally as the induction time increases, however, this behavior is not observed under microwave and ultrasound activation. We can say that in addition to the thermal microwave effect, a non-thermal microwave effect is present in the system.
authors.affiliation: Laboratorio de Fisicoquıímica Macromolecular, Facultad de Química, Universidad Nacional Autónoma de México, Edificio "D" 108, Ciudad Universitaria, México 04510, D.F., C.P., Mexico; E-Mail:  polylab1@servidor.unam.mx.
authors.forename: Hugo Mendoza
authors.initials: HM
authors.lastname: Tellez
authors.forename: Joaquín Palacios
authors.initials: JP
authors.lastname: Alquisira
authors.forename: Carlos Rius
authors.initials: CR
authors.lastname: Alonso
authors.forename: José Guadalupe López
authors.initials: JG
authors.lastname: Cortés
authors.forename: Cecilio Alvarez
authors.initials: CA
authors.lastname: Toledano
mesh_terms: D000812:Anhydrides / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry*; D003959:Diamines / Q000737:chemistry; D004146:Dioxanes / Q000737:chemistry; D007700:Kinetics; D008872:Microwaves; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D013010:Sonication; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D000812:Anhydrides; D001555:Benzene Derivatives; D003959:Diamines; D004146:Dioxanes; D011108:Polymers; C513053:polyamic acid
references.citation: Ultrason Sonochem. 2008 Jan;15(1):89-94
references.pmid: 17382571
references.citation: Chem Soc Rev. 2005 Feb;34(2):164-78
references.pmid: 15672180
references.citation: Ultrason Sonochem. 2004 Jul;11(5):301-6
references.pmid: 15157859
references.citation: Ultrason Sonochem. 2007 Sep;14(6):680-8
references.pmid: 17291813
references.citation: Angew Chem Int Ed Engl. 2004 Nov 26;43(46):6250-84
references.pmid: 15558676
references.citation: Ultrason Sonochem. 2007 Sep;14(6):689-94
references.pmid: 17275390
references.citation: J Phys Chem B. 2010 Mar 11;114(9):3178-84
references.pmid: 20151653
references.citation: Ultrason Sonochem. 2006 May;13(4):364-70
references.pmid: 16014337