Bis 2 4 6 trimethylbenzoyl phenylphosphineoxide

The LCN actuators are made by photopolymerization of a mixture containing 52 mol% of LC monomer 4-Methoxybenzoic acid 4-(6-acryloyloxyhexyloxy)phenyl ester (Synthon Chemicals), 18 mol% of LC monomer 4[4[6-Acryloxyhex-1-yl)oxyphenyl]carboxybenzonitrile (Synthon Chemicals), 21 mol% of di-acrylate crosslinker 1,4-Bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene (Synthon Chemicals), 6 mol% of azo crosslinker 4,4’-Bis[9-(acryloyloxy)nonyloxy]azobenzene (Synthon Chemicals), 1.5 mol% of 1,4-Bis(methylamino)anthraquinone (Disperse Blue 14, Sigma Aldrich) and 1.5 mol% of photoinitiator Bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (Sigma Aldrich). All molecules were used as received. The monomer mixture was dissolved in dichloromethane and filtered through PTFE syringe filter (Sigma Aldrich, pore size 0.2 µm), after which it was stirred at 80 °C (100 RPM) for 3 h in order to remove the solvent.

LC monomers 4-Methoxybenzoic acid 4-(6-acryloyloxyhexyloxy)phenyl ester (MAPE), 4[4[6-Acryloxyhex-1-yl)oxyphenyl]carboxybenzonitrile (AOCB), 1,4-Bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene (AOBM), 4,4′-Bis[9 -(acryloyloxy)nonyloxy]azobenzene (A9ZA9) were acquired at Synthon Chemicals (Wolfen,, Germany), and the photoinitiator Bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide from Sigma Aldrich (St. Louis, MO, USA). Elvamide was provided by Beamco (Supplementary Figure S2). The ZnO nanopowder was bought from Sigma Aldrich (Aldrich Cod 544906—average particle size 71 nm—specific surface area 15 m²/g).

Polyvinyl alcohol (PVA) filaments were obtained from eSUN (Shenzhen, China). Polyethylene glycol diacrylate (PEGDA, average MW 575 g/mol), bis (2,4,6-trimethylbenzoyl) phenylphosphineoxide and riboflavin (MW 376.36 g/mol) were purchased from Sigma Aldrich Ltd. (Dorset, UK). Kollicoat IR, a copolymer of polyvinyl alcohol and polyethylene glycol (approx. MW 45,000 Da) was obtained from BASF (Stockport, UK). Candurin^® Gold Sheen was purchased from Merck (Dorset, UK). All materials were used as received.