2 bromoacetophenone

Model acrylate emulsion polymers were synthesized using radical emulsion polymerization of methyl methacrylate (MMA, Sigma Aldrich), n-butyl acrylate (BA, Sigma Aldrich), n-butyl methacrylate (BMA, Sigma Aldrich) and acrylic or methacrylic acid (AA or MAA, Sigma Aldrich), as outlined in Table 1. Sodium lauryl sulphate (32% in water, VWR, Amsterdam, The Netherlands) was used as emulsifier and ammonium persulphate (Evonik, Marl, Germany) as initiator. The samples are dispersed in water to approximately 30% by weight. Ammonia (25% in water, VWR) was used in a stoichiometric equivalent of 0.7 to partly neutralize the acid groups.
n-Methylpyrrolidone (NMP, peptide synthesis grade) and tetrahydrofuran (THF, uLCMS grade) were purchased from Biosolve (Valkenswaard, The Netherlands). Triethylamine (TEA, 99.5%), hydrochloric acid (HCl, 37%), N-methylmorpholine (NMM, >99%), chloro-dimethoxytriazine (CDMT, >98%), ethyl chloroformate (ECF, >99%), propyl chloroformate (PCF, >99%), 3-nitrobenzyl chloroformate (NBCF, >96%), p-bromophenacyl bromide (pBPB, 99.8%), p-nitrophenacyl bromide (pNPB, >98%) and 2-bromoacetophenone (PB, 99%) were purchased from Sigma-Aldrich (Zwijndrecht, The Netherlands).

All chemicals were used as received. Polyethyleneglycol diacrylate (PEG-DA) (MW ∼ 258), PEG-DA (MW ∼ 575), 3-(trichlorosilyl)propyl methacrylate (TPM); trichloromethane, butyl acrylate, 1,3-butanediol diacrylate, 3-(trimethoxysilyl)propyl methacrylate, 2-acryl-amido-2-methyl-1-propanesulfonic acid (AMPS), 2,2-dimethoxy-2-phenylacetophenone (DMPA), ammonium acetate, thiourea, 2-bromoacetophenone, 1-heptanal and trypsin from bovine pancreas (12 443 BAEE units per mg protein) were purchased from Sigma-Aldrich (Steinheim, Germany). Elastosil E43 was obtained from Wacker Chemie (Munich, Germany). Acetonitrile (Rotisolv HPLC gradient grade) and ethanol were acquired from Carl Roth (Karlsruhe, Germany). Buffer solutions were prepared using ultrapure water.