SYNTHETIC HAIR CONDITIONING POLYMERS 23 No polymer CELLOSIZE™ QP 10 0MH UCARE™ JR-400 (PQ-10) UCARE™ LR-30M (PQ-10) UCARE™ JR-30M (PQ-10) SOFTCAT™ SL-5 (PQ-67). Five shampoo formulations were pre pared with these fi ve commercial polymers, whereas a reference shampoo formulation was prepared without any conditioning polymer. Hair tresses were treated with these formulations and evaluated for wet combing via the auto- mated tensile tester. Example wet-combing curves for shampoos containing PQ-67 and no polymer are shown in Figure 2A. The areas under the curves for all samples were integrated using the “trapezoid rule,” and the resulting values, representing wet combing work in N-mm, are shown in Figure 2B. The ranking of commercial polymers via the automated wet combing method showed reasonable correlation (within experimental error) to the known ranking aforementioned. It was concluded that this method could also yield a valid ranking for the synthetic poly- mers. Thus, several hundred cationic polymers were synthesized from a variety of vinyl monomers and screened for performance, with the objective of identifying synthetic vinyl monomer-based polymers that exhibit conditioning performance greater than that of the current commercially available semi-synthetic conditioning polymers. Figure 2. (A) Example wet-combing curves for hair tresses treated with shampoos formulated with conditioning polymer PQ-67 (two samples “with PQ-67,” or SL-5), and without any conditioning polymer (two samples “no polymer”). (B) Automated wet-combing work for hair tresses treated with shampoos containing commercial conditioning polymers. Four or more replicates were used unless otherwise noted. Dark bars are error bars.

JOURNAL OF COSMETIC SCIENCE 24 RATIONALE FOR DESIGN OF EXPERIMENT S (DOEs) AND WORKFLOW A DOE approach was used in plannin g the polymer syntheses. The DOEs were designed to screen a wide range of polymer compositions to optimize shampoo performance across wet comb, wet feel, and clarity properties. Thus, polymer composition, molecular weight, solubility parameter (balance of hydrophobic and hydrophilic monomer composition), and type and density of cationic charge were systematically varied. High throughput tools were used to make the hypothesized polymers. Key classes of monomers chosen for this study were (i) cationic quat monomers (DADMAC, APTAC, AETAC, and QMA at 65, 80, and 95 wt% of the polymer), (ii) hydrophobic monomers (MMA, BA, LMA, and SMA at 0, 2.5, and 5 wt% of the polymer), and (iii) hydrophilic amide (AAm and DMAAm, at 0, 15, and 30 wt% of the polymer) and amine (DMAEMA and DMAEA at 0, 15, and 30 wt% of the polymer) monomers. Scheme 1 shows the general workfl ow used in the synthesis and screening of the conditioning polymer candidates. Synthesis was followed by SEC analysis, polymer drying, and determination of solubility (presence or absence of haze), viscosity (in 2 wt% aq. solution), % polymer solids in each reaction mixture, and monomer conversion. In this preliminary initial screening effort, the effect of monomer reactivity ratios on polymer composition was not studied in detail effects such as this will need to be dealt with in more in depth follow-up work. We do not, however, anticipate major departures from the overall polymer composition predicted on the basis of the composi- tion of the monomer mixture. Shampoos were formulated with polymers that showed high monomer conversions and little-to-no haze (indicating potential for solubility in a clear shampoo) in the reaction medium. Wet combing work was then determined for hair tresses treated with these shampoos. Results at each stage were used to determine the design of the next series of polymer libraries, as shown in Scheme 1. In this preliminary study, the focus was on comb performance in a single shampoo base. Polymers were synthesized by free- radical polymerizations of different classes of vinyl monomers. Scheme 2 outlines the overall path leading to the fi nal polymer candidate iden- tifi cation. Three DOEs were conducted: the fi rst to identify an advantageous cationic mono- mer, the second to evaluate the effect on conditioning of hydrophobic monomers, and the third to evaluate amide and amine monomers on conditioning performance. DOE-1 probed the composition space of polymers containing different cationic quat mono- mers. Libraries in this DOE consisted of mixture designs where four classes of monomers were varied for a given quat monomer. The following range of monomers (in wt% of total monomers) was used in DOE-1: 65–95% quat monomer, 0–30% amine (DMAEA or DMAEMA), 0–30% AAm, and 0–5% BA. Each library in this initial DOE contained the same set of 24 monomer compositions, with the only difference being in the selection of the type of quat monomer. Example output data are shown in Table III. Shampoo formulations Scheme 1. Overview of the workfl ow used for high throughput polymer synthesis and evaluation.