Shape-memory PCL films were prepared by crosslinking tetra-branched PCL with acrylate end-groups in the presence of linear PCL telechelic diacrylates.30 (link),31 Briefly, two-branched and four-branched PCL were synthesized by a ε-caprolactone (CL) (Tokyo Kasei Kogyo Co, Ltd, Tokyo, Japan) ring-opening polymerization that was initiated with tetramethylene glycol (Wako Pure Chemical Industries, Ltd, Osaka, Japan) and pentaerythritol (Tokyo Kasei Kogyo Co, Ltd) as initiators, respectively. Acryloyl chloride (Tokyo Kasei Kogyo Co, Ltd) was then reacted with the end of the branched chains. The structures and the molecular weights were estimated by nuclear magnetic resonance (1H NMR) spectroscopy (JEOL, Tokyo, Japan) and gel permeation chromatography (JASCO International Co, Ltd, Tokyo, Japan). The obtained PCL macromonomers were dissolved in xylene containing benzoyl peroxide (BPO; Sigma-Aldrich, St Louis, MO, USA) and the solution was injected between a glass slide with a 0.2 mm thick Teflon spacer. The PCL macromonomers were cured for 180 minutes at 80°C.
1h nmr spectroscopy
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1H NMR spectroscopy is a analytical technique that uses a magnetic field to measure the resonance of hydrogen nuclei in a sample. It provides information about the structure and composition of organic compounds.
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3 protocols using 1h nmr spectroscopy
1
Synthesis of Shape-Memory PCL Films
2
Synthesis and Characterization of Crosslinked P(CL-co-DLLA) Copolymers
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Four-branched copolymers poly(ε-caprolactone-co-D,L,lactide) (P(CL-co-DLLA) were synthesized as described in our earlier reports 14 , 15 (link). The structure and molecular weights were determined by 1H NMR spectroscopy (JEOL, Tokyo, Japan) and gel permeation chromatography (GPC; JASCO International, Tokyo, Japan) respectively. The viscoelastic spectrum (storage modulus, G' and loss modulus, G'') of the substrate was tested as a function of frequency and temperature using a rheometer (MCR 301, Anton Paar, Tokyo, Japan). The non-crosslinked P(CL-co-DLLA) substrate for cell culture was prepared by a spin-coating technique as described in our previous report 14 . Crosslinked substrate was prepared by thermal crosslinking P(CL-co-DLLA) macromonomers as mentioned in our previous reports 14 ,15 (link). The mechanical property of the crosslinked substrate was characterized by a tensile test (EZ-S 500N; Shimadzu, Kyoto, Japan). Scanning electron microscope (SEM) images of crosslinked and non-crosslinked P(CL-co-DLLA) substrates were examined with SU-8000 (Hitachi, Japan).
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Synthesis and Characterization of Four-Branched Copolymers
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The synthesis of four-branched copolymers of ε-caprolactone and D,L, lactide (DLLA) of 60:40 ratio of 100 or 500 unit length was performed as described in our earlier reports [21 (link),22 (link)]. The molecular weights and structure of the polymers were estimated by GPC (JASCO International, Tokyo, Japan) and 1H NMR spectroscopy (JEOL, Tokyo, Japan), respectively. The viscoelastic properties of non-crosslinked P(CL-co-DLLA) substrates were tested using a rheometer (MCR 301, Anton Paar, Tokyo, Japan) and a viscoelastic spectrum which measured storage modulus (G’) and loss modulus (G’’).
Four-branched P(CL-co-DLLA) 100 or 500 units were dissolved in toluene at different concentration ranges from 1 w/v% to 100 w/v%. The solutions were then mixed with a small proportion of nile red (TCI America) and spin coated on 15 mm glass coverslip at 15,000 rpm for 60 sec. For cell culture, four-branched P(CL-co-DLLA) 100 or 500 units were dissolved in toluene at 80 w/v% and 50 w/v% respectively. The prepared P(CL-co-DLLA) substrates were then spin-coated on glass coverslips of 24-well inserts (15 mm) or 6-well inserts (35 mm) as described above and sterilized using a low-pressure hydrogen peroxide gas plasma system CH-160C (Toho Seisakusho, Tokyo, Japan).
Four-branched P(CL-co-DLLA) 100 or 500 units were dissolved in toluene at different concentration ranges from 1 w/v% to 100 w/v%. The solutions were then mixed with a small proportion of nile red (TCI America) and spin coated on 15 mm glass coverslip at 15,000 rpm for 60 sec. For cell culture, four-branched P(CL-co-DLLA) 100 or 500 units were dissolved in toluene at 80 w/v% and 50 w/v% respectively. The prepared P(CL-co-DLLA) substrates were then spin-coated on glass coverslips of 24-well inserts (15 mm) or 6-well inserts (35 mm) as described above and sterilized using a low-pressure hydrogen peroxide gas plasma system CH-160C (Toho Seisakusho, Tokyo, Japan).
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