Poly(methyl methacrylate-co-ethyl acrylate) latex particles with poly(ethylene glycol) grafts: structure and film formation.
Water-based copolymer dispersions were prepared using methyl methacrylate (MMA), ethyl acrylate (EA) (MMA/EA = 1:2), and a series of nonionic polymerizable surfactants, i.e., "surfmers" based on poly(ethylene glycol)-(meth)acrylates. The latexes were compared with the behavior of a conventionally stabilized (nonionic nonylphenol ethoxylate, NP100 with 84 ethylene oxide units) dispersion with the same MMA-EA composition (PMMAEA). A number of techniques were employed in order to characterize structure, dynamics, and film formation properties: solution/solid-state NMR, dynamic/static light scattering (DLS/SLS), differential scanning calorimetry (DSC), tensile/shear mode dynamic mechanical thermal analysis (DMTA), and atomic force microscopy (AFM). The surfmers were found to be miscible with the MMA-EA copolymer at room temperature, with 46-85 mol % of the reacted surfmer detected at the particle surfaces, and the remaining part buried in the particle bulk. In contrast, the NP100 surfactant formed a separate interphase between the copolymer particles with no mixing detected at room temperature or at 90 degrees C. For a 4.0% dry weight concentration, NP100 phase separated and further crystallized at room temperature over a period of several months. Composition fluctuations related to a limited blockiness on a length scale above approximately 2 nm were detected for PMMAEA particles, whereas the surfmer particles were found to be homogeneous also below this limit. On a particle-particle level, the dispersions tended to form colloidal crystals unless hindered by a broadened particle size distribution or, in the case of PMMAEA, by the action of NP100. Finally, a surface roughness (Rq) master plot was constructed for data above the glass transition temperature (Tg) from Tg + 11 degrees C to Tg + 57 degrees C and compared with the complex shear modulus over 11 frequency decades. Shift factors from the 2 methods obeyed the same Williams-Landel-Ferry (WLF) temperature dependence, thus connecting the long-time surface flattening process to the rheological behavior of the copolymer.
Schantz
Staffan
S
PAR and D, AstraZeneca R and D, S-43183 Mölndal, Sweden. staffan.schantz@astrazeneca.com
Carlsson
Hans T
HT
Andersson
Thomas
T
Erkselius
Stefan
S
Larsson
Anders
A
Karlsson
Ola J
OJ
D003102:Colloids / Q000737:chemistry; D008863:Microspheres; D011092:Polyethylene Glycols / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000138:chemical synthesis* / Q000737:chemistry; D012212:Rheology
D003102:Colloids; D011109:Polymethacrylic Acids; D011092:Polyethylene Glycols