Fluorocarbon-containing hydrophobically associating thickener
时间:2005-05-17
Yunxiang Zhang*, Aihua Da
Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences
354 Fenglin Road, Shanghai 200032, China
Corresponding author. Tel.: +86-21-6416-3300 ext. 3131; Fax: +86-21-64166128,
E-mail: zhangyx@pub.sioc.ac.cn
1. Introduction
Water-soluble polymers especially hydrophobically modified water-soluble polymers (HMWSP) which bear a small amount of hydrophobes on the hydrophilic backbone are important for their wide industrial application in both coatings and cosmetics and their interactions with surfactants in aqueous solution have been extensively studied.1 In last two decades, with more research focused on the associative thickeners replacing the traditional celluloses in some waterborne coatings. In our group, a series of hydrocarbon and fluorocarbon hydrophobically modified polyelectrolytes were synthesized and their associative behaviors were detail investigated.2,3 It was found that the incompatibility between CF and CH groups in the micellization process was improved in solution of both CF and CH co-modified poly(acrylic acid). Based on these results, it was discovered that the terpolymer could be used as a novel thickener for coating, medical and cosmetics industry. In this presentation, we try summary main results and show the possibilities of being used as associative thickeners and being brought about industrialization.
2.Experimental
2.1. Synthesis
For the typically hydrophobically associative property, the structures of copolymer are shown in Scheme 1. The hydrophobically modified poly (acrylic acid) was synthesized from precipitation copolymerization of acrylic acid with a hydrophobic comonomer in benzene. Details are described as in previous papers.2,3 Molecular structures of four surfactants are shown in Scheme 2..
2.2. Viscosity Characterization
The Brookfield viscometric measurements were performed on a Wells Brookfield viscometer equipped with two different sizes of spindles (18# and 34#) r. All viscosity values reported in this paper are given for a shear rate of 0.4s-1 and the temperature was controlled at 25±0.2℃during measurements.
2.3. Rheological measurement
Rheological experiments of polymer solutions were carried out on a HAAK Rheostress RS 75 rheometer equipped with a 2o/6 cm cone-plate geometry. A C60/2Ti sensor was adopted and the gap was kept 0.108 mm.
3. Results and discussions
3.1. Dilute solution properties of the copolymers
The dilute solution properties of the copolymers were studied in their sodium salt form. The intrinsic viscosity of FMPAANa in aqueous NaCl solutions is governed by the competition of the electrostatic repulsion between negative carboxyl groups and intramolecular hydrophobic association between fluorocarbon groups. At low NaCl concentration, the electrostatic repulsion is strong enough to suppress the intramolecular association. Therefore, the modified polyelectrolyte displays similar intrinsic viscosity to the unmodified polyelectrolyte. At high NaCl concentration,however, the electrostatic repulsion is screened and both the intramolecular association and the intermolecular association are enhanced.
3.2. Influence of the hydrophobes on the viscosity of copolymer
The hydrophobically modified copolymers and terpolymers were synthesized using long chain alkyl CH, CF or both of CH and CF as hydrophobic comonomers. It was found the stronger aggregation of CF group than CH analogs and CH group will be enhanced the association in the terpolymer which contains the both of CH and CF branch.
3.3 Interaction of the polymer with surfactants
Interactions between hydrophobically modified polyelectrolytes and oppositely charged surfactants was studied and shown strong interactions The surfactant molecules are usually absorbed onto the microdomains or form micelles by self-aggregation, thus the interaction can be enhanced or reduced upon addition of surfactants, which can be reflected by significant change of rheological properties. It was found that the non-iononic surfactant strongly interacts with CF modified polymers, especially for terpolymers.
3.4. Rheological property and mechanism of thickener
Recently a new class of associative thickeners has been proposed for use in high-solids, non-aqueous coatings. Contrary to their counterparts as being used in waterborne coatings, the associative thickener used in solvent-borne coatings results in a pseudoplastic flow behavior. The thickening action of both types of associative thickeners and film properties are discussed in detail.
4. Conclusion
CF or CH modified and both of CF and CH co-modified polyelectrolyte PHF has been synthesized and especially the association of PHF’s solution with a nonionic surfactant Np7.5 is detail investigated by rheological measurements. Strong aggregates with the core containing both CH and CF hydrophobiles are produced in the solution of PHF by adding Np7.5. The poor compatibility between CH surfactant and CF containing polyelectrolytes is improved in PHF/Np7.5. Based on these results, it was discovered that the terpolymer could be used as a novel thickener for coating, medical and cosmetics industry. The application research of the associative thickener is in progress.
Acknowledgements
NSF of China (No. 59973025) is gratefully acknowledged for the financial support of this research and also authors thank for Department of Macromolecular Sciences and Key Laboratory of Molecular Engineering of Polymer, Fudan University for using HAAK Rheostress RS75 rheometer.
REFERENCES.
1. Interactions of surfactants with polymers and proteins; Goddard, E. D.; Anathapadmanabhan, K. P., Eds.; CRC press: Boca Raton, 1993.
2. Zhang, Y. X.; Da, A. H.; Butler, G. B.; Hogen-Esch, T. E. J Polym Sci, Part A: Polym Chem 1992, 30, 1383.
3. a. Zhuang, D. Q.; Cao, Y.; Zhang, H. D.; Yang, Y. L.; Zhang, Y. X. Polymer 2002, 43, 2075.
b. Zhuang, D. Q.; Guo, J. F.; Zhang, Y. X. Macromol Rapid Comm 2002, 23, 109.
论文来源：Asia Polymer Symposium(APOSYM/2004)October 10-16
