689-02-1Relevant articles and documents
Investigation of the telomerization kinetics of N-isopropylacrylamide using 3-mercaptopropionic hydrazide as chain transfer agent
Costioli, Matteo D.,Berdat,Freitag, Ruth,Andre, Xavier,Mueller, Axel H. E.
, p. 3630 - 3637 (2005)
The telomerization (chain transfer polymerization) kinetics of N-isopropylacrylamide were investigated in various (hydro)organic solvents using 3-mercaptopropionic hydrazide as chain transfer agent (telogen). Except for the dioxane/water system telogen consumption rates were similar for all cases, while solvent effects could be observed for the monomer consumption rates. Chain transfer constants, as defined by the ratio of the rate constants for chain transfer and chain propagation (CT = ktr/kp), were highest in DMF (10.3), a solvent unable to form hydrogen bonds or dipole-dipole interactions with the monomer, while a more promising value of CT = 1.7 was found for the 6:4 methanol/water mixture. The highest monomer consumption rates were observed for the 1:1 dioxane/water mixture. However, in this particular case the telogen consumption was also found to increase, as we propose due to a "hydrophobic effect" whereby polymer microaggregates serve to locally increase the concentration of telogen and/or monomer once a certain water concentration has been passed. As a result a comparatively high CT of 3.2 characterizes the dioxane/water system.
A stimulus-responsive poly-pyrrole nano tube targeted drug carrier and its preparation method
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Paragraph 0067; 0068, (2020/02/07)
The invention provides a stimulus-response type polypyrrole nanotube targeting drug carrier and a preparation method. A titanium dioxide nanotube array or a porous anodic alumina array serves as a template, and a polypyrrole nanotube is prepared through chemical vapor deposition; beta-cyclodextrin and a tube opening of a polypyrrole nanotube are connected through stimulus response type sensitive bonds such as acyl hydrazone bonds and disulfide bonds, and medicine can be blocked in the nanotube and released out in the faintly acid and reducibility environments; one end of a polyethylene glycol chain is connected with a folic acid targeted molecule, the other end of the polyethylene glycol chain is connected with an adamantane head base, the adamantane head base is linked up to a beta-cyclodextrin hydrophobic cavity through host and guest envelope, and folic acid molecules recognize tumor cells through a receptor-ligand medium. The stimulus-response type polypyrrole nanotube targeting drug carrier prepared through the method is uniform in particle diameter size distribution, controllable in appearance, stable in product, simple in synthesis process, low in cost and suitable for mass production.
Design, synthesis, and operation of small molecules that walk along tracks
Von Delius, Max,Geertsema, Edzard M.,Leigh, David A.,Tang, Dan-Tam D.
supporting information; experimental part, p. 16134 - 16145 (2011/02/16)
The synthesis and system dynamics of a series of small-molecule walker-track conjugates, 3,4-Cn (n = 2, 3, 4, 5, and 8), based on dynamic covalent linkages between the "feet" of the walkers and the "footholds" of the track, is described. Each walker has one acyl hydrazide and one sulfur-based foot separated by a spacer chain of "n" methylene groups, while the track consists of four footholds of alternating complementary functionalities (aldehydes and masked thiols). Upon repeatedly switching between acid and base, the walker moiety can be exchanged between the footholds on the track, primarily through a "passing-leg gait" mechanism, until a steady state, minimum energy, distribution is reached. The introduction of a kinetically controlled step in the reaction sequence (redox-mediated breaking and reforming of the disulfide linkages) can cause a directional bias in the distribution of the walker on the track. The different length walker molecules exhibit very different walking behaviors: Systems n = 2 and 3 cannot actually "walk" along the track because their stride lengths are too short to bridge the internal footholds. The walkers with longer spacers (n = 4, 5, and 8) do step up and down the track repeatedly, but a directional bias under the acid-redox conditions is only achieved for the C 4 and C5 systems, interestingly in opposite directions (the C8 walker has insufficient ring strain with the track). Although they are extremely rudimentary systems, the C4 and C5 walker-track conjugates exhibit four of the essential characteristics of linear molecular motor dynamics: processive, directional, repetitive, and progressive migration of a molecular unit up and down a molecular track.
