Azoisobutyronitrile

Nanofibrillated cellulose hydrogel (2%) was prepared as previously reported using a mechanical homogenization method [37 ,38 (link)]. Nanocrystalline cellulose hydrogel (11.9%) was purchased from the Process Development Center, University of Maine. m-Cresol, lithium chloride, N,N-dimethylacetamide, chlorobenzene, phenol, polyethylenimine (PEI) (number average molecular mass Mn = 60 kg/mol), maleic acid (MA), sodium hypophosphite, glycidyl methacrylate (GMA, 97%), azoisobutyronitrile (AIBN), oligo (ethylene glycol) methyl ether methacrylate (OEGMA, Mn = 950 g/mol, stabilized with inhibitors), and inhibitor removers (kits for removing hydroquinone and monomethyl ether hydroquinone (MEHQ) and tert-butylcatechol (BHT)) were purchased from Sigma-Aldrich (St. Louis, MO, USA).
Silicon wafers (100 crystal plane) with a native oxide layer were purchased from University Wafer (South Boston, MA, USA). A polyethylene terephthalate (PET) film (0.50 mm thick) and a nylon 6,6 (PA 6,6) film (0.5 mm thick) were purchased from GoodFellow, Coraopolis, PA, USA. A cellophane film (regenerated cellulose) 0.03 mm thick was provided by Thermetrics. Cotton (100%, plain weave), nylon 6,6 (100%, spun, plain weave), cotton/polyester, PET (50%/50%, plain weave), polyester, and PET (100%, spun, plain weave) fabrics were purchased from Testafabrics, Inc., West Pittston, PA, USA.

After the μCT scan bone histology was performed to investigate the micro-architecture of the callus.
For calcified histology the bones were fixed in 10 % neutral buffered formalin for 14 days at room temperature, dehydrated with ascending concentrations of ethanol and embedded in methylmethacrylate for 5 days at 4 °C.
Afterwards the tissue was soaked in methyl methacrylat monomer, nonpylphenyl-polyethyleneglycol acetate and azoisobutyronitrile (all from Sigma-Aldrich, St. Louis, USA). The blocks were released from the glass vials and sections of 40 μm were sawed and grinded using an EXAKT diamond saw system (Exakt, Norderstedt, Germany). The samples were lubricated with 0.1 % formic acid for 2 minutes and washed with water afterwards. The sections were submerged in 20 % methanol for one hour and stained with toluidine blue or haematoxylin and eosin.

Styrene, AT (97%), PVP (M_w = 360,000), and azoisobutyronitrile were purchased from Sigma-Aldrich (St. Louis, MO, USA). 2-Propanol (>99.5%) was purchased from TCI (Shanghai, China) Development Co., Ltd. CuCl₂∙2H₂O (99%) was obtained from Sinopharm Chemical Reagent (Shanghai, China). The Styrene monomer was purified by passing it through a basic aluminum oxide column. All other chemicals were used as received.