scholarly journals Incorporation of titanate nanosheets to enhance mechanical properties of water-soluble polyamic acid

2020 ◽  
Author(s):  
Christian Harito ◽  
Dmitry V Bavykin ◽  
Frank C Walsh
Keyword(s):  
Colloidal Dispersion ◽  
Filler Loading ◽  
Water Soluble ◽  
Nanocomposite Films ◽  
Polyamic Acid ◽  
Theoretical Predictions ◽  
Solid Film ◽  
Nanoindentation Hardness ◽  
Polyimide Precursor ◽  
Titanate Nanosheets

Pyromeliticdianhydride (PMDA) and 4’,4’-oxydianiline (ODA) were used asmonomers of polyimide. To synthesise a water soluble polyimide precursor (polyamic acidsalt), triethylamine (TEA) was added to polyamic acid with a TEA/COOH mole ratio of 1:1.Titanate nanosheets were synthesised by solid-state reaction, ion-exchanged with acid, andexfoliated by TEA. Exfoliated titanate nanosheets were mixed with water soluble polyamicacid salt as reinforcing filler. Drop casting was deployed to synthesise polyamic acid/titanatenanosheet nanocomposite films. Scanning electron microscopy (SEM) and transmissionelectron microscopy (TEM) were employed to study the morphology and dispersion ofnanosheets in the colloidal dispersion and the solid film composite. Modulus and hardness ofnanocomposites was provided by nanoindentation. Hardness increased by 90% with addition of2% TiNS while modulus increased by 103% compared to pure polymer. This behaviour agreeswell with Halpin-Tsai theoretical predictions up to 2 wt% filler loading; agglomeration occursat higher concentrations.

scholarly journals Polyamic Acid Nanofibers Produced by Needleless Electrospinning

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Oldrich Jirsak ◽  
Petr Sysel ◽  
Filip Sanetrnik ◽  
Jakub Hruza ◽  
Jiri Chaloupek
Keyword(s):  
Pressure Drop ◽  
Ir Spectroscopy ◽  
Polyamic Acid ◽  
Needleless Electrospinning ◽  
Electrospinning Method ◽  
Filtration Properties ◽  
To Receive ◽  
Polyimide Precursor ◽  
Oxydiphthalic Anhydride

The polyimide precursor (polyamic acid) produced of4,4′-oxydiphthalic anhydride and4,4′-oxydianiline was electrospun using needleless electrospinning method. Nonwoven layers consisting of submicron fibers with diameters in the range about 143–470 nm on the polypropylene spunbond supporting web were produced. Filtration properties of these nanofiber layers on the highly permeable polypropylene support—namely filtration effectivity and pressure drop—were evaluated. Consequently, these polyamic acid fibers were heated to receive polyimide nanofibers. The imidization process has been studied using IR spectroscopy. Some comparisons with the chemically identical polyimide prepared as the film were made.

Chemistry of Adhesion at the Polyimide-Metal Interface

1987 ◽  
Vol 108 ◽  
Author(s):  
M. Grunze ◽  
W. N. Unertl ◽  
S. Gnanarajan ◽  
J. French
Keyword(s):  
Structural Changes ◽  
High Vacuum ◽  
Scanning Tunneling ◽  
Metal Interface ◽  
Polyimide Films ◽  
Absorption Data ◽  
Polyamic Acid ◽  
Vapor Phase Deposition ◽  
Infrared Reflection ◽  
Polyimide Precursor

ABSTRACTThis article describes recent studies of the chemistry of adhesion between thin (d ≥ 11 Å) polyimide films and silver and copper substrates, and the structural changes in the polymer when polyamic acid is imidized to polyimide. The thin polyamic acid films were formed by vapor phase deposition of 1,2,4,5-benzenetetracarboxylic anhydride (PMDA) and 4,4-oxydianiline (ODA) under high vacuum conditions and subsequent imidization by heating in vacuum. Both ODA and PMDA are at least partially dissociated upon adsorption onto clean copper and silver and with increasing film thicknesses react to form the polyimide precursor, polyamic acid. Heating to T ≥ 425 K leads to polymerization to form polyimide films which are thermally stable to about 700 K. Polyimide films with mean thicknesses as small as 1.1 nm have been fabricated in this way and their bonding to the substrate as determined by x-ray photoemission studies is su marized. Infrared reflection absorption data gives further evidence that the polyimide bonds to the substrate via fragmented PMDA. Changes in the surface topography and molecular structure of the films during imidization are demonstrated by scanning tunneling micrographs and infrared reflection absorption data.

The preparation of new poly(phenylsilsesquioxane)-polyimide hybrid films by the sol-gel process and their properties

1994 ◽  
Vol 6 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Yoshitake Iyoku ◽  
Masa-aki Kakimoto ◽  
Yoshio Imai
Keyword(s):  
Nmr Spectra ◽  
Sol Gel ◽  
Tensile Modulus ◽  
Heating Process ◽  
Hybrid Films ◽  
Polyamic Acid ◽  
Sol Gel Process ◽  
Polyimide Matrix ◽  
Polyimide Precursor ◽  
Silicone Content

The preparation of poly(phenylsilsesquioxane)-polyimide hybrid films was successfully performed with phenyltriethoxysilane (PhTES) and the polyamic acid (polyimide precursor) prepared from 4.4'-oxydianiline (ODA) and pyromellitic dianhydride (PMDA). During the heating process at 300 C, the imidization of the polyamic acid and the sol-gel reaction, hydrolysis and condensation of PhTES, proceeded simultaneously. The IR spectrum and the t3C-NMR and 29Si-NmR spectra showed that the sol-gel reaction of PhTES proceeded in the polymer matrix with high conversion. The hybrid films with a silsesquioxane content up to 75 wt% were obtained as the self-standing form. The hybrid films having a silsesquioxane content of 45 wt% were yellow and transparent, and those having more silicone content were yellow and translucent. The therma] properties of the hybrid films were improved to some extent by the introduction of the silsesquioxane component into the polyimide matrix. With respect to the tensile properties. the tensile strength remained around 85 MPa up to a silicone content of 45 wt%. This value was twice that of the hybrid films based on methyltriethoxysilane. The tensile modulus decreased with increasing silsesquioxane content.

Stability of nano-sized permethrin in its colloidal state and its effect on the physiological and biochemical profile of Culex tritaeniorhynchus larvae

2017 ◽  
Vol 107 (5) ◽  
pp. 676-688 ◽  
Author(s):  
P. Mishra ◽  
A.P.B Balaji ◽  
P.K. Dhal ◽  
R.S. Suresh Kumar ◽  
S. Magdassi ◽  
...  
Keyword(s):  
Mosquito Species ◽  
Colloidal Dispersion ◽  
Water Soluble ◽  
Control Treatment ◽  
Oil In Water ◽  
Pyrethroid Pesticide ◽  
Instability Rate ◽  
Colloidal State ◽  
The Mean ◽  
And Control

AbstractThe occurrence of pesticidal pollution in the environment and the resistance in the mosquito species makes an urge for the safer and an effective pesticide. Permethrin, a poorly water-soluble pyrethroid pesticide, was formulated into a hydrodispersible nanopowder through rapid solvent evaporation of pesticide-loaded oil in water microemulsion. Stability studies confirmed that the nanopermethrin dispersion was stable in paddy field water for 5 days with the mean particle sizes of 175.3 ± 0.75 nm and zeta potential of −30.6 ± 0.62 mV. The instability rate of the nanopermethrin particles was greater in alkaline (pH 10) medium when compared with the neutral (pH 7) and acidic (pH 4) dispersion medium. The colloidal dispersion at 45°C was found to be less stable compared with the dispersions at 25 and 5°C. The 12- and 24-h lethal indices (LC50) for nanopermethrin were found to be 0.057 and 0.014 mg l−1, respectively. These results were corroborative with the severity of damages observed in the mosquito larvae manifested in epithelial cells and the evacuation of the midgut contents. Further, the results were substantiated by the decrease in cellular biomolecules and biomarker enzyme activity in nanopermethrin treated larvae when compared to bulk and control treatment.

Preparation and Drug Release Studies of Chitosan/Methoxy Poly(Ethylene Glycol)-b-Poly(D,L-Lactide-co-Glycolide) Nanocomposite Films for Use as Controlled Release Drug Delivery

2008 ◽  
Vol 55-57 ◽  
pp. 717-720 ◽  
Author(s):  
N. Niamsa ◽  
M. Srisa-ard ◽  
Y. Srisuwan ◽  
N. Kotsaeng ◽  
Y. Baimark ◽  
...  
Keyword(s):  
Drug Release ◽  
Ethylene Glycol ◽  
Diblock Copolymer ◽  
Diblock Copolymers ◽  
Chitosan Film ◽  
Water Soluble ◽  
Nanocomposite Films ◽  
Poly Ethylene Glycol ◽  
Chitosan Films ◽  
Poly Ethylene

Nanocomposite chitosan-based films incorporated with drug-loaded methoxy poly(ethylene glycol)-b-poly(D,L-lactide-co-glycolide) diblock copolymers (MPEG-b-PDLLG) nanoparticles were prepared by forming drug-loaded nanoparticles in chitosan solution before suspension-solution film casting. Salicylic acid was used as a poorly-water soluble model drug. The nanocomposite films with DLL/G ratios of 100/0 and 85/15 mol% and chitosan/diblock copolymer/drug ratios of 80/1/1, 80/2/2 and 80/4/4 (w/w) were prepared and investigated. The sizes of drug-loaded nanoparticles into the chitosan films were approximate or less than 100 nm. Nanopores were observed in the resulted chitosan films incorporated with drug-loaded nanoparticles when the diblock copolymer ratio was increased up to 2. Number and size of the nanopores increased as increasing the diblock copolymer ratio. Only the nanocomposite films with chitosan/diblock copolymer/drug ratio of 80/1/1 (w/w) showed slower drug release than the chitosan film.

Water soluble nanocomposite films based on poly(vinyl alcohol) and chemically modified montmorillonites

2013 ◽  
Vol 48 (5) ◽  
pp. 545-553 ◽  
Author(s):  
Teresa M Pique ◽  
Claudio J Pérez ◽  
Vera A Alvarez ◽  
Analía Vázquez
Keyword(s):  
Vinyl Alcohol ◽  
Water Soluble ◽  
Nanocomposite Films ◽  
Poly Vinyl Alcohol ◽  
Chemically Modified
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