Methyl violet

Bisphenol A (BPA) used as A₂ monomer for preparing the in-situ generated DGEBA monomer was purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan) and was purified by recrystallization from toluene before using. Epichlorohydrin (ECH) as epoxidation reagent was obtained from Tokyo Chemical Industry Co., Ltd. Pentaerythritol (PE) used as B₄ branch generating unit for reacting with the in-situ generated DGEBA was purchased from Tokyo Chemical Industry Co., Ltd., Japan and was purified by recrystallization from ethanol prior to use. Polyethylene glycol (PEG400, Mw = 400 g/mol) as A₂ monomer was purchased from Sigma-Aldrich, St. Louis, MI, USA. Sodium hydroxide (NaOH) as base catalyst and sodium chloride (NaCl) were obtained from Ajax Finechem, Australia. Hydrobromic acid (HBr), acetic acid, potassium hydrogen phthalate, methyl violet, and chlorobenzene were used to determine epoxy equivalent weight (EEW) of the hyperbranched epoxy resins and were purchased from Tokyo Chemical Industry Co., Ltd., Japan. Diethylenetriamine (DETA) as amine curing agent was brought from Tokyo Chemical Industry Co., Ltd., Japan. Solvents were analytical grades and used as received.

DGEBA, having an epoxy equivalent weight (EEW) of 170.21 g eq⁻¹, (Sigma-Aldrich, St. Louis, MO, USA) was used as the main base of epoxy resin in the formulated mixture. Hyperbranched epoxy resin was synthesized and characterized via FTIR and NMR techniques. The results are shown in Figures S1 and S2, respectively. The chemical for the synthesis: BPA (Tokyo Chemical Industry Co., Ltd., Tokyo, Japan) was used as an aromatic monomer, and was purified via recrystallization using toluene before use. PEG400, Mw = 400 g/mol, (Sigma-Aldrich, St. Louis, MO, USA) was used as an aliphatic monomer. Epichlorohydrin (ECH), (Tokyo Chemical Industry Co., Ltd., Tokyo, Japan) was used as an epoxidation reagent. PE (Tokyo Chemical Industry Co., Ltd., Tokyo, Japan) was used as a branch generating unit and was recrystallized with ethanol before use. Sodium hydroxide (NaOH) as a base catalyst and sodium chloride (NaCl) were obtained from Ajax Finechem, Sydney, Australia. Hydrobromic acid (HBr), acetic acid, potassium acid phthalate, methyl violet, and chlorobenzene (Tokyo Chemical Industry Co., Ltd., Tokyo, Japan) were used to determine the epoxy equivalent weight (EEW) following the standard test methods (ASTM D 1652) [23 ]. Triarylsulfonium hexafluorophosphate salts (Sigma-Aldrich, St. Louis, MO, USA) were used as a photoinitiator.