Degradable, Dendritic Polyols on a Branched Polyphosphazene Backbone

Abstract

Herein, we present the design, synthesis, and characterization of fully degradable, hybrid, star-branched dendritic polyols. First multiarmed polyphosphazenes were prepared as a star-branched scaffold which upon functionalization produced globular branched hydroxyl-functionalized polymers with over 1700 peripheral functional end groups. These polyols with unique branched architectures could be prepared with controlled molecular weights and relatively narrow dispersities. Furthermore, the polymers are shown to undergo hydrolytic degradation to low molecular weight degradation products, the rate of which could be controlled through postpolymerization functionalization of the phosphazene backbone.

Stimuli‐Responsive Phosphorus‐Based Polymers

“…These polymers were shown to have pH stimulated degradation profiles that was significantly faster at pH 5 than pH 7, with further acceleration when the pH is reduced to 2. A similar pattern was observed for polyphosphazene‐based dendritic polyols (Figureàb), as well as solid porous matrices …”

“…(a) The proposed mechanism for pH‐catalyzed polyphosphazene chain cleavage and (b) Rate of phosphate release from the main‐chain of polyphosphazene‐based polyols as observed by a photometric phosphate assay. Adapted from ref …”

Main-Chain Phosphorus-Containing Polymers for Therapeutic Applications

“…Furthermore, polyphosphazenes can also be grafted from polymers bearing arylphoshines as initiating points to generate star-branched and brush architectures [41]. For example, a combination of this with thiol-yne post-polymerization functionalization has been used to prepare highly branched polyols (Figure 9) [42].…”

Mesoporous Silica Micromotors with a Reversible Temperature Regulated On–Off Polyphosphazene Switch

“…In the first step of the micromotor preparation, bipyridine ligands equipped with four organosilane‐functionalities (SiBPy) were anchored through covalent SiOSibonds within the walls of the mesochannels during co‐condensation with TEOS yielding functional MPSiBBy microparticles. To obtain this trimethoxysilane ligand (SiBPy), thiol‐yne addition of 3‐mercaptopropyl trimethoxysilane was used to link the triple bonds of the prepared bipyridine derivative BPy‐alkyne (for experimental details see Supporting Information). Afterward, a mixture of TEOS and the corresponding synthetized silane‐derived bipyridine (SiBPy) in molar ratio 95:5 was used.…”

“…The second polyphosphazene (PPz2) was characterized by 1 H and 31 P NMR spectroscopy (see Figures S4 and S5, Supporting Information). The third step was the preparation of PPz3, whereby 11‐mercaptoundecanoic acid was reacted by a photoinduced thiol‐yne addition reaction to lower the LCST values of the resultant materials, which were measured to be ≈35 °C for PPz2, however, for PPz3 a visible clouding was observed 10 °C lower, ≈25 °C (Figure S7, Supporting Information). Finally, for adding the required alkoxysilane groups that will permit the grafting of the polymer onto the silanols of the silica particles surface, the last step consisted of the reaction of 3‐mercaptopropyl trimethoxysilane with the remaining propargylamine groups onto the polyphosphazene, also via thiol‐yne addition to give a trimethoxysilane‐functionalized polymer, so‐called PPz4.…”