The synthesis of functional polyphosphazenes and their surfaces

Abstract

The macromolecular substitution approach for the synthesis of polyphosphazenes provides access to many different polymers. However, it precludes the use of reagents that contain two or more functional groups because such compounds would cause extensive crosslinking of the chains. This presents a problem because many of the uses for which polyphosphazenes seem ideally suited require the presence of-OH,-COOH,-NH 2 ,-SO 3 H,-PR 2 and other functional units in the side-chain structure. We have developed two approaches to introduce such active sites: (1) protection-deprotection reactions; and (2) direct reactions of active reagents with the organic side-groups of non-functional poly(organophosphazenes). These methods have been applied both at the molecular level and in the form of reactions carried out only at polymer surfaces. The resultant polymers have special properties that are valuable in the microencapsulation of sensitive biological agents; in the formation of hydrophobic, hydrophilic, or adhesive surfaces; in crosslinking reactions; and in the development of solid polymer electrolytes, bio-erodible polymers, pH-triggered hydrogels, polymer blends and interpenetrating polymer networks. Overall, more than 700 different polyphosphazenes are now known, and a large number of these are functional macromolecules targeted for specific property combinations and uses.

Biodegradable Polyphosphazene Biomaterials for Tissue Engineering and Delivery of Therapeutics

“…Next, the organic side chains are attached to the polymer backbone through a nucleophilic macromolecular substitution of the organic substituents for the phosphorus-bound chlorine atoms [18, 21, 26]. The following two sections succinctly will describe the individual steps of polyorganophosphazene synthesis showing the vast range of materials that can be generated.…”

Synthesis and characterization of a new hybrid polyphosphazene containing two symmetrical polyhedral oligomeric silsesquioxane (POSS) units

“…[13][14][15] Polyphosphazenes consist of the linear backbone of alternating phosphorus and nitrogen atoms and two organic side groups linked to each phosphorus atom. 16 Various polyphosphazenes have been fabricated by introducing different side groups or by changing the feed ratios of the side groups. 17,18 The applications of polyphosphazenes have primarily focused on fire retardants, solid polymer electrolytes and biomaterials.…”

Second-order nonlinear optical properties of polyphosphazenes containing multi-dipolar and imidazolebased chromophores

“…They present a number of useful features for practical devices, such as the excellent flexibility of the backbone, high thermal and oxidative stability, optical transparency from 220 nm to the near-IR region, and controlled covalent incorporation of chromophores can be easily accomplished over a broad concentration range. Recently, some new synthetic routes [20][21][22][23][24][25][26] have been developed for the preparation of polyphosphazenes with large molecular hyperpolarizabilities and high glass-transition temperatures.…”