SYNTHETIC HAIR CONDITIONING POLYMERS 19 polymer phase behavior and shampoo formulation (32,33). In this initial study, ex- perimental design methods enabled by high throughput combinatorial methods were used in a broad polymer design, synthesis, and focused screening effort that led to the identifi cation of synthetic cationic conditioning polymer candidates that show con- ditioning performance (combability, silicone deposition, wet feel, etc.) similar to or greater than that of PQ-67 in limited and preliminary performance screens. Further work will be needed to understand polymer performance in a wider range of formula- tions and treatment conditions. EXP ERIMENTAL METHODS MAT ERIALS APT AC, AETAC, DADMAC, QMA, 2-(dimethylamino)ethyl acrylate (DMAEA), 2-(dimethylamino)ethyl methacrylate (DMAEMA), acrylamide (AAm), N,N-dimethyl- acrylamide (DMAAm), butyl acrylate (BA), methyl methacrylate (MMA), lauryl acrylate (LA), lauryl methacrylate (LMA), stearyl methacrylate (SMA), tert-butyl hydroperoxide (TBHP), sodium 1-hydroxymethanesulfonate (sodium formaldehyde sulfoxylate, SFS), and citric acid were purchased from Sigma-Aldrich (St. Louis, MO) (see Figure 1 for the structures of the monomers). Surfactants sodium laureth-2 sul- fate (SLES-2 primary anionic surfactant) and disodium cocoamphocarboxyglycinate (amphoteric surfactant) were purchased from Cognis (Cincinnati, OH). Dimethylol- dimethylhydantoin (DMDMH 55 preservative broad-spectrum bactericide) was obtained from Lonza (South Plainfi eld, NJ). Hair care polymers CELLOSIZE™ QP 100MH, UCARE™ JR-400 (PQ-10), UCARE™ LR-30M (PQ-10), UCARE™ JR-30M (PQ-10), and SOFTCAT™ SL-5 (PQ-67) were obtained from the Dow Chemical Company (Midland, MI). Cationic guar was obtained from Rhodia (Houston, TX). The silicone emulsion DC 1664 was purchased from Dow Corning (Midland, MI). Hair tresses (8 h bleached hair) were purchased from International Hair Importers and Products (White Plains, NY). Figure 1. Chemical structures of vinyl monomers used in this study.

JOURNAL OF COSMETIC SCIENCE 20 POLYMER SYNTHESIS All poly mers in this study were synthesized using a semi-continuous parallel pressure reac- tor (ScPPR FreeSlate, Sunnyvale, CA). This reactor consists of three metal blocks (A, B, and C), each containing eight cells (A1–A8 in block A, B1–B8 in block B, and C1–C8 in block C), enabling 24 parallel polymer syntheses. A glass insert with 10 mL total volume (6 mL working volume) was placed into each cell. Each cell was supplied with eight feed lines, and therefore, up to eight liquid components (monomers, initiators, and solvents) could be de- livered to each of the 24 inserts through the feed lines. A set of computer-controlled pumps and valves controlled the addition of these components and enabled delivery of different volumes into each insert. Reaction mixtures were mechanically stirred using plastic impel- lers, and the reactor blocks were heated to the desired temperature. In a typ ical polymerization, aqueous solutions of APTAC (1.17 g APTAC), DMAEMA (0.43 g DMAEMA), and AAm (0.11 g AAm) were used, as well as a 15-wt% dioxane solution of BA (0.09 g BA). The total amount of monomers in a run was 1.80 g. TBHP and SFS were used as an initiator redox pair they were added in amounts of 0.60 wt% and 0.30 wt%, respectively, relative to the total amount of monomers. The fi nal volume of the reaction mixture (including water) was 6.0 mL at 30% (wt/v) solids. Batch and semi- batch protocols for monomer addition were used in this work. In a typical batch process, all monomers were loaded into the inserts at the beginning of the run. The mixture was heated to 55°C with stirring, and the initiator (TBHP/SFS) was added over 4 h at 55°C, followed by heating at 55°C and stirring for an additional hour. In a typical semi-batch process, 30% of the monomers were added at the beginning of the run, and the mixture was heated to 55°C while stirring at 400 rpm (revolutions per minute). The remaining 70% of the monomers were added over 4 h at 55°C with stirring, with the initiator (TBHP/SFS) being added over that same 4-h period. The reaction mixture was then stirred at 55°C for an additional hour. Polymers were dried in vacuo. MONOMER CONVER SION The amounts of residual monomers in the polymerization mixtures were determined by high pressure liquid chromatography using a Luna C18 4.6 mm × 150 mm, 3 μm column, and a Luna C18 3 mm × 4 mm guard column (Phenomenex, Torrance, CA). Water and acetonitrile containing 0.08% trifl uoroacetic acid were used as a mobile phase, with the following gradient at 1.0 mL/min with UV detection (at 195, 205, or 215 nm). Monomer convers ions were 93% in all cases. POLYMER MOLECULAR W EIGHT The weight average molecular weight, Mw, and polydispersity (PDI) of the polymers were deter- mined relative to narrow poly(ethylene oxide) standards in aqueous solution using size exclusion