Polyphosphazenes – Synthetically Versatile Block Copolymers (“Multi‐Tool”) for Self‐Assembly

Abstract

This microreview outlines recent advances on the synthesis and self-assembly of polyphosphazene diblock copolymers, a class of versatile polymers (Multi-Tool) able to generate a great variety of different well-defined nanomorphologies. Particular focus is placed on the synthesis of linear block copolymers composed of two polyphosphazene chains (PP-b-PP′), or hybrid polymers combining one PP chain with a non- [a] 2484 Gabino A. Carriedo (Ph D in 1981) is Full-time Professor of Inorganic Chemistry in the University of Oviedo since 1989. His research interest in synthetic chemistry has included coordination and organometallic chemistry, electrochemistry and polymer chemistry. Since 1995 he has focused in designed syntheses of phosphazene polymers and their chemical derivatization. (2012) developing new synthetic methodologies in organic chemistry by means of organometallic carbene reagents under the supervision of Prof. J. Barluenga and Prof. J. Flórez. After, she moved to the group of D. Dixon (Oxford) to explore new catalytic asymmetric methodologies. She returned to the University of Oviedo in 2015 as Post-doctoral research assistant. Nowadays, her research is focused on the synthesis and self-assembly of new material based on polyphosphazene polymers. 2488 Scheme 4. Synthesis of linear polyphosphazene diblock copolymers 28-35 by sequential living cationic polymerization of phosphoranimines of type (X)(R 1 )(R 2 )P=N-SiMe 3 over living chains of 1[PCl 6 ]. Scheme 5. Sequential living polymerization of phosphoranimine 36 by using active end-groups of polyphosphazene 17 as initiators. The synthesis of BCP 37 is suggested in ref. 47. methodologies afforded the PP-b-PS copolymers with moderately good yields (< 60 %) and polydispersities (< 1.3). Scheme 10. Synthetic routes to polyphosphazene-b-polystyrene, PP-b-PS, via macromolecular coupling of telechelic (PS) n -P(R) 2 = N-SiMe 3 , 53 and 54, with an end-capped poly(dichlorophosphazene) 55 (Ec. c). Raquel de la Campa was born in Cangas del Narcea (Asturias, Spain) in 1981. He obtained his PhD at the University of OviedoRecently, our group developed a very convenient synthesis for linear hybrid PP-b-PS block copolymers (Scheme 11). [63] Using the lithiated-phosphine 56 as initiator, the anionic polymerization of styrene gave the telechelic polystyrene 57 (PS m -PPh 2 ) after quenching the reaction with Cl-SiMe 3 . The chlorination of Scheme 11. Synthetic routes to polyphosphazene-b-polystyrene, PP-b-PS (60), via lithiated-phosphine initiator 56, and macromolecular initiator 58.2492 57 led to PS m -PPh 2 Cl 2 (58) having -PPh 2 Cl 2 end-groups that initiate the polymerization of Cl 3 P=N-SiMe 3 (6) producing the block copolymer [N=PCl 2 ] n -PS m (59). The macromolecular substitution of the chlorine atoms by -OCH 2 CF 3 groups yielded the block copolymer [N=P(OCH 2 CF 3 ) 2 ] n -PS m (60) having crystalline PP blocks. This synthetic methodology afforded the hybrid PP-b-PS block copolymer in 70 % yield and with narrower polydispersities (PDI = 1.2) than those of the...

Main-Chain Phosphorus-Containing Polymers for Therapeutic Applications

“…This can be carried out in one pot directly from PCl 3 (Figure 3A), hence without tedious purification of the intermediates [16], which is suitable for upscaling, albeit with some loss of control. More recently, it has been shown that starting from Ph 3 PCl 2 , monodirectional growth can be ensured [17], as shown in Figure 3B, which is a feature that opens the door to the development of chain-end functionalized polyphosphazenes [18], as well as higher architectures such as polyphosphazene block copolymers [19], block copolymers with organic macroinitiators [20], and star-branched and bottle-brush polyphosphazenes [21]. Similarly, the development of controlled routes to polyphosphoesters has led to a recent surge in their development [22].…”

“…The higher stability compared to liposomes renders them ideal drug carriers [54]. Furthermore, Soto and coworkers have developed, amongst other nanomorphologies [19], giant polymersomes, so-called giant unilamellar vesicles (GUVs) with good stability over a long time range [57]. Giant polymersomes (approximately 10-100 µm) and GUVs (>1 µm) as opposed to standard polymersome sizes in the region of 100 nm diameters are of special interest due to their similar size to cells making them better suited to the biomimicry of cellular processes.…”

Stimuli‐Responsive Phosphorus‐Based Polymers

“…Since polyalkylphosphazenes are not sensitive to hydrolysis due to their stable P–C bonds, morphological changes occur without degradation of the polymer. A recent review article describes the advances in the field of self‐assembly of this family of polymers …”

“…Selective protonation of polyphosphazene block copolymers induces rapid self‐assembly. Reproduced from ref and adapted from original work in ref …”

Dynamic Polyphosphazene Networks with Modulating Shape Memory and Self‐Healing Capacity by Double Coordination Interactions

“…Polyphosphazene is a unique class of hybrid polymers with an amazing structural design. [ 1,2 ] It has a wide range of applications in high‐performance elastomers such as low‐temperature elastomers, [ 3–5 ] flame‐retardant materials, [ 6–8 ] stretchable electronics, [ 9,10 ] bionic muscles, [ 11,12 ] super‐hydrophobic materials, [ 13,14 ] and biodegradable materials. [ 15–17 ] However, there are few reports about recyclable and self‐healing polyphosphazene, while similar studies are popular in polysiloxane.…”