Andrea Vallieri - Academia.edu (original) (raw)
Papers by Andrea Vallieri
Polymer Bulletin, 1992
Multiblock-(A-B)n-copolymers containing polyester segments together with perfluoropolyether (PFPE... more Multiblock-(A-B)n-copolymers containing polyester segments together with perfluoropolyether (PFPE) segments have been prepared by polymerizing dimethyl terephthalate (DM'r), or an oquimolar mixture of DMT and dimethyl isophthalate (DMI), with ethylene glycol (EG) in the presence of different telechelic perfiuoropolyethers in various amounts (5-30 wt%), using Ti(OBu)4 as the catalyst. Fomblin ZDEAL (a-COOCH3 terminated PFPE), Fomblin ZDOL (a PFPE having-CH2OH terminal groups), and Fomblin ZDOLI~X (a PFPE having-CH20(CH2CH20)yH terminal groups) were used as telechellc PFPEs. Fomblin ZDOLTX gave the best results: the highest yield in block copolymer (less sensitive to hydrolysis with respect to block copolymers prepared from the other PFPEs), a longer average length of polyester segments, and a relatively low fraction of PFPE lost by distillation during polymerization. In troduction Perfluoropolymers are characterized primarily for their excellent thermal and chemical stability, inertness, durability, low coefficient of friction, low wettability etc, and are widely used in special applications. These Include biomedical applications, lubrication of magnetic media, electrical insulation In the microelectronic indus1W etc. Perfluoropolyethers (PFPE), in particular, are viscous liquids characterized for their very low glass transition (Tg =-120oc). A series of telechelic pertluoropolyethers having different types of terminal groups has been made available under the trade name of Fomblln by Montefluos; these Include the types used in the present paper, namely, Fomblin ZDEAL, Fomblln ZDOL and Fomblin ZDOLTX, having formula I with X =-COOCH3, CH2OH and-CH20(CH2CH20)yH, respectively. X-CF20((C2F40)n-(CF20)m]CF2-X (1) These terminal groups make them potential comonomers for preparing block copolymers containing perfluoropolyether blocks. In previous papers(I,2) we characterized the polymeric materials obtained by polymerizing dimethyl terephthalate (DMT) and ethylene glycol (EG) in the presence of Fomblin ZDEAL under various experimental conditions. In any case, the polymeric materials consisted of poly(ethylene terephthalate) homopolymer (PET), PET-PFPE multlblock copolymers and unreacted PFPE. The fraction of unreacted PFPE decreased, relatively to the overall PFPE content, by decreasing the initial amounts of ZDEAL, however, even for an initial amount of ZDEAL as low as 5%, there was still a 50% of PFPE unreacted. Therefore, It is practically Impossible to obtain a large amount of PET-PFPE multiblock copolymer directly from polymerization when Fomblln ZDEAL Is used. Other drawbacks, connected with the use of FombUn ZDEAL, are a low hydrolytic stability of the ester bonds at the junction between polyester and PFPE segments, and the Inhibition of the catalytic activity of the catalysts(1,2) usually employed for the first stage, of transesterlfication, of polymerization of PET. For this last reason Fomblin ZDEAL has to be added when the first stage is completed, before starting the second stage. It was also Interesting to note that the very surface compastton of samples prepared with the polymeric materials obtained from the polymerization of PET In the presence of FombUn ZDEAL was much richer in fluorine than the bulk composition(3), and that the surface composition profile was dependent on the relative amount of unreacted PFPE(4). In order to verify the possibility of preparing samples with an high amount of polyester-PFPE multiblock copolymers, we have extended the study to other PFPEs, and in this paper we report the results of polymerizations of polyesters (PET) and copolyesters (from DMT, DMI and EG) carded out In the presence of Fomblin ZDEAL, Fomblin ZDOL and Fomblin ZDOLTX.
Inorganica Chimica Acta, 1995
Polymer Bulletin, 1992
Multiblock-(A-B)n-copolymers containing polyester segments together with perfluoropolyether (PFPE... more Multiblock-(A-B)n-copolymers containing polyester segments together with perfluoropolyether (PFPE) segments have been prepared by polymerizing dimethyl terephthalate (DM'r), or an oquimolar mixture of DMT and dimethyl isophthalate (DMI), with ethylene glycol (EG) in the presence of different telechelic perfiuoropolyethers in various amounts (5-30 wt%), using Ti(OBu)4 as the catalyst. Fomblin ZDEAL (a-COOCH3 terminated PFPE), Fomblin ZDOL (a PFPE having-CH2OH terminal groups), and Fomblin ZDOLI~X (a PFPE having-CH20(CH2CH20)yH terminal groups) were used as telechellc PFPEs. Fomblin ZDOLTX gave the best results: the highest yield in block copolymer (less sensitive to hydrolysis with respect to block copolymers prepared from the other PFPEs), a longer average length of polyester segments, and a relatively low fraction of PFPE lost by distillation during polymerization. In troduction Perfluoropolymers are characterized primarily for their excellent thermal and chemical stability, inertness, durability, low coefficient of friction, low wettability etc, and are widely used in special applications. These Include biomedical applications, lubrication of magnetic media, electrical insulation In the microelectronic indus1W etc. Perfluoropolyethers (PFPE), in particular, are viscous liquids characterized for their very low glass transition (Tg =-120oc). A series of telechelic pertluoropolyethers having different types of terminal groups has been made available under the trade name of Fomblln by Montefluos; these Include the types used in the present paper, namely, Fomblin ZDEAL, Fomblln ZDOL and Fomblin ZDOLTX, having formula I with X =-COOCH3, CH2OH and-CH20(CH2CH20)yH, respectively. X-CF20((C2F40)n-(CF20)m]CF2-X (1) These terminal groups make them potential comonomers for preparing block copolymers containing perfluoropolyether blocks. In previous papers(I,2) we characterized the polymeric materials obtained by polymerizing dimethyl terephthalate (DMT) and ethylene glycol (EG) in the presence of Fomblin ZDEAL under various experimental conditions. In any case, the polymeric materials consisted of poly(ethylene terephthalate) homopolymer (PET), PET-PFPE multlblock copolymers and unreacted PFPE. The fraction of unreacted PFPE decreased, relatively to the overall PFPE content, by decreasing the initial amounts of ZDEAL, however, even for an initial amount of ZDEAL as low as 5%, there was still a 50% of PFPE unreacted. Therefore, It is practically Impossible to obtain a large amount of PET-PFPE multiblock copolymer directly from polymerization when Fomblln ZDEAL Is used. Other drawbacks, connected with the use of FombUn ZDEAL, are a low hydrolytic stability of the ester bonds at the junction between polyester and PFPE segments, and the Inhibition of the catalytic activity of the catalysts(1,2) usually employed for the first stage, of transesterlfication, of polymerization of PET. For this last reason Fomblin ZDEAL has to be added when the first stage is completed, before starting the second stage. It was also Interesting to note that the very surface compastton of samples prepared with the polymeric materials obtained from the polymerization of PET In the presence of FombUn ZDEAL was much richer in fluorine than the bulk composition(3), and that the surface composition profile was dependent on the relative amount of unreacted PFPE(4). In order to verify the possibility of preparing samples with an high amount of polyester-PFPE multiblock copolymers, we have extended the study to other PFPEs, and in this paper we report the results of polymerizations of polyesters (PET) and copolyesters (from DMT, DMI and EG) carded out In the presence of Fomblin ZDEAL, Fomblin ZDOL and Fomblin ZDOLTX.
Inorganica Chimica Acta, 1995