Synthesis of hydroxypropyl cellulose derivatives modified with amphiphilic diblock copolymer side-chains for the slow release of volatile molecules

Hydroxypropyl cellulose (HPC) was used as carrier material to prepare comb-like grafted block copolymers having an amphiphilic core-shell structure. The hydroxyl groups of HPC were partially protected with trimethylsilyl groups and the free OH groups used to initiate the ring opening polymerisation (ROP) of L-lactide. The end-chain of the grafted hydrophobic poly(L-lactide) (PLLA) chain was then functionalised with 2-bromopropionyl bromide which was used to polymerise the tert-butyl acrylate ((t)BA) monomer by atom transfer radical polymerisation (ATRP). The hydrophobic P(t)BA block was then hydrolysed to a hydrophilic poly(acrylic acid) (PAA) block. The resulting amphiphilic grafted copolymer HPC-g-(PLLA-b-PAA) was dissolved in an ethanol/water mixture (9:1), such as a typical Eau de Toilette (EdT) formulation. Atomic force microscopy (AFM) and size measurements confirmed the presence of core-shell structures in solution. A significant swelling of HPC-g-(PLLA-b-PAA) in the presence of a volatile bioactive molecule, methyl 2,2-dimethyl-6-methylene-1-cyclohexanecarboxylate (Romascone (R)), was observed by dynamic light scattering (DLS). Furthermore, the presence of HPC-g-(PLLA-b-PAA) significantly decreased the evaporation rate of Romascone (R), thus serving as an efficient fragrance delivery system in formulations with high ethanol content.