Effect of Polymer Composition on Polymer Diffusion in Poly(butyl acrylate-co-methyl methacrylate) Latex Films

Abstract

We describe polymer diffusion measurements in poly(butyl acrylate-co-methyl methacrylate) [P(BA-MMA)] copolymer latex films by fluorescence resonance energy transfer (FRET). Four sets of copolymers were prepared from various weight ratios of butyl acrylate and methyl methacrylate by semicontinuous emulsion polymerization. Their glass transition temperatures range from 4 to 28 °C. Latex particles were labeled with phenanthrene (Phe) as the donor dye and with 4-(N,N-dimethylamino)benzophenone (NBen) as the acceptor dye. Latex films were cast from a 1:1 mixture of Phe-and NBen-labeled latex samples. Polymer diffusion was monitored as a function of annealing temperature, and apparent diffusion coefficients (D app ) were calculated from the energy transfer data using a simple diffusion model. These values increased with annealing temperature and decreased with T g . Rheology measurements recorded the response of the dynamic moduli (G′, G′′) with respect to oscillatory shear frequency (ω) over a range of temperature close to that of the diffusion experiments. The temperature dependence of polymer dynamics extracted by the rheology experiments is in good agreement with the temperature dependence of D app . Increasing the BA copolymer content leads to an apparent increase in long-chain branching, which is reflected in both the time dependence of D app and in the dynamic moduli measurements. A greater degree of branching leads to a broader distribution of polymer diffusion coefficients and a stronger time dependence of D app . Experimental SectionMaterials. Potassium persulfate (KPS), sodium carbonate (Na 2 -CO 3 ), and 1-dodecanethiol (C 12 -SH) were used as received from Aldrich. Polystep A-16 (22% solution of dodecylbenzene and tridecylbenzenesulfonates, 1 Stepan Co., Maywood, NJ) and methylβ-cyclodextrin were kindly supplied by Rohm and Haas Co. and used as received. Methyl methacrylate (MMA, Aldrich), butyl acrylate (BA, Aldrich), and methacrylic acid (MAA, Aldrich) were distilled at reduced pressure, and the purified monomers were stored at 0 °C until use. Water was purified by a Milli-Q ion-exchange filtration system. Phenanthrylmethyl methacrylate (PheMMA) was used as received from Toronto Research Chemicals Inc. 4′-Dimethylamino-2-methacryloxy-5-methylbenzophenone (NBenMA) was synthesized as described elsewhere. 4,5 Latex Preparation. All latex dispersions were prepared by semicontinuous emulsion polymerization reactions. A typical recipe for the synthesis of nonlabeled P(BA-MMA) (BA:MMA weight ratio 60:39) latex is shown in Table 1. In the first stage, a dispersion of seed particles was prepared by batch emulsion polymerization

The onset of polymer diffusion in a drying acrylate latex: how water initially retards coalescence but ultimately enhances diffusion

“…The general recipe is given in Table 1, and the details are reported elsewhere. 11 Donor-labeled particles were prepared in the presence of 1 mol% phenanthrylmethyl methacrylate (Phe-MA); acceptorlabeled particles were prepared in the presence of 0.3 mol% 4¢-dimethylamino-2-methacryloxy-5-methyl benzophenone (NBen-MA). Glass transition temperatures on dried polymer samples were measured with a TA Instruments Q100 differential scanning calorimeter (DSC).…”

“…This sort of behavior is typical, and is thought to reflect the effects of polydispersity in molecular weight 22 and the effects of longchain branching. 11,23 For low extents of mixing, the interdiffusion process is dominated by lower molecular weight and faster diffusing polymers. As the extent of mixing increases, higher molecular weight and highly branched species begin to contribute more to the time dependence of U ET , hence the extracted value of D decreases.…”

Effect of alkali-soluble resin emulsifiers on coalescence and interdiffusion between latex polymer particles

“…The polymer interdiffusion process was monitored following the evolution of the fluorescence decay profile I D (t). The results were given in terms of the quantum efficiency of energy transfer (ϕ ET ), which is related to the fraction of molecular mixing in a system of labelled particles, and it is defined as [25][26][27][28]:…”

Isolation of the effect of the hairy layer length on the mechanical properties of waterborne coatings

“…Thus, ˚E T can be related to the fraction of molecular mixing in a system of labelled particles and it is defined as shown in Eq. (2) [31,33,[36][37][38]:…”

“…Another useful parameter is the extent of mixing, f m (t), expressed in terms of the increase in energy transfer, normalized by the maximum change associated with complete mixing [31,33,[36][37][38]:…”