【正文】 for the conventionally used CMC. Initial examinations[20] have indicated that the novel latex can form film without theaddition of coalescing solvents, which, as suggested above, on one hand would provide an alternative method for the production of VOCfree architectural coat ings and, on the other, would ply with the stringent EU and DEFRA regula tions.[21]Materials and MethodsThree aqueous latex positions, sup plied by ICI Plc, based on copolymers of methyl methacrylate (MMA) and 2ethyl hexyl acrylate (2EHA) were studied. In this paper the latices stabilised with carbox ymethyl cellulose (CMC) will be referred to as standardlow and high Tg。 Co. KGaA, Weinheim 122Macromol. Symp. 2009, 281, 119–125Figure 2.ESEM images of a standardlow Tg latex specimen during film formation。 273 K, (b) T 188。 K.III/IV. In the final Stage IV (Figure 2c) all particles appear to have lost their identities and only topographical features due to defects and/or impurities can be seen within the structure of the polymer film. Based on the above results, which are parable to those obtained in previous studies[1–5], it can be said that the film formationmechanism of the standardlow Tg acrylic latex is in a good agreement with the conventional descriptions.Standard Latex – High TgThe ESEM results for the film formation mechanism of the standardhigh Tg latex are presented in Figure 3. The structure of the latex at the early stages of the drying process is similar to the standard–low Tg latex and consists of individual randomly distributed polymer particles in contact with each other. However, due to the fact that the glass transition temperature of the latex is much higher than the temperaturesFigure 3.ESEM images of standard–high Tg latex during drying。 276 K) of film formation particles form arrays (indicated by arrows) with hexagonal and fourfold symmetry。 Co. KGaA, Weinheim Macromol. Symp. 2009, 281, 119–125 123Figure 4.ESEM images of novel acrylic latex at (a) T 188。 276 K.at which film formation was observed in the ESEM, it was found that upon drying the particles did not deform and/or coalesce, but formed wellordered arrays. The end result was the formation of a colloidal crystal, within the surface plane of which the majority of the packing was found to have hexagonal symmetry, although occa sionally fourfold symmetry was also observed (Figure 3a). At lower magnifica tions (Figure 3b) the packing is seen to have many defects, both in terms of ‘missing’ particles and in terms of grain boundaries where the orientation of the planes changes.Novel LatexThe results for the film formation mechan ism of the novel acrylic latex are presented in Figure 4 (a, b). It is clearly seen that under ‘wet’ conditions (Figure 4a) the microstructure of the specimen consists of individual particles and clusters with sizes in the range 2–5 mm. The presence of these clusters was also confirmed by particle size measurements carried out by ICI Plc using a Coulter LS230 light scattering apparatus. Due to the fact that the spherical particles with diameters of ca. 300 nm are still physically distinct, . no significant coales cence has taken place, it can be said that the latex is in Stage II/III of the film formation process.Figure 4b reveals the microstructure of the specimen at a temperature of 276 K. It is evident that at this temperature, significant water evaporation has taken place, which has resulted in the formation of a discon tinuous film with voids present within itsstructure. The fact that not all particles have pletely lost their identities, sug gests that the latex is in Stage III/IV.Due to the fact that imaging of the latex specimens was carried out below their Tg of280 K, it is somewhat surprising to observethe latter stages of film formation. How ever, it is suggested that as the microstruc tural analysis was carried out at tempera tures very close to the minimum film formation temperature (T 188。 . the distance between beam exit point and cluster is shorter than the distance between beam exit point and polymer film.The accumulation of clusters on the surface of the latex specimens can beCopyright 2009 WILEYVCH Verlag GmbH amp。 D 。 6pmRTaking m as water viscosity 10 3 Ns/m2,kT as 4 10 21 J and E as 3 10 8 m/s then,Pe 1011 H R。 Surf. A: Physico chem. Eng. Aspects 174, 2000, 37–53.[7] D. J. Stokes, Philos. Trans. R. Soc. Lond., A 361, 2003,2771–2787.[8] R. E. Cameron, A. M. Donald, J. Microscopy 173, 1994,227.[9] G. L. Brown, J. Polym. Sci. 22, 1956, 423.[10] J. W. Vanderhoff, Br. Polym. J. 2, 1970, 161.[11] S. S. Voyutakii, Z. M. Ustinova, J. Adhes. 9, 1977,39.[12] D. P. Sheettz, J. Appl. Polym. Sci. 9, 1965, 3759–3773.[13] E. M. Boczar, B. C. Dionne, Z. Fu, A. B. Kirk, P. M. Lesko, A. D. Koller, Macromolecules 26, 1993,5772.Copyright 2009 WILEYVCH Verlag GmbH amp。 Co. KGaA, Weinheim