Multiarm Core Cross-Linked Star-Shaped Poly(2-oxazoline)s Using a Bisfunctional 2-Oxazoline Monomer

Abstract

Poly(2-oxazoline)s are an attractive class of polymers that have a potential for biomedical applications. However, synthetic approaches for the preparation of 2-oxazoline-based star-shaped polymers are quite limited and are usually based on either end-capping of a living chain with a multifunctional terminator or utilizing a multifunctional initiator. Up until now, the use of a bisoxazoline monomer as a cross-linking agent for the synthesis of core cross-linked star shaped poly(2-oxazoline) polymers has not been reported. Herein, we have developed a new bis-oxazoline cross-linker via a fast and efficient thiol click reaction with no catalyst and purification required. Moreover, we have utilized this cross-linker to prepare well-controlled core cross-linked star polymers with poly(2-oxazoline) arms in a straightforward manner. Synthesized star-shaped polymers were characterized in detail using an advanced gel permeation chromatography technique and were found to have a range of arms from <10 to over 1000. Furthermore, the effect of the reaction concentration, amount of cross-linker, and arm length on star formation were analyzed and the stars' potential for dihydroxyanthroquinone encapsulation was explored.

Degradable thioester core-crosslinked star-shaped polymers

“…By measuring samples of known concentration, information on the concentration and specific viscosity at different molecular weights can be obtained from the refractive index (RI) and the viscosity (VS) detectors respectively. 10,33 Equations S1 and S2 (cf. supporting information) were used to calculate the intrinsic viscosity (IV) and the branching factor g' whilst Equations S3 and S4 were used to estimate the average number of arms, f (n) .…”

“…As the degree of branching increases, the molecular weight increases but the molecular size in solution does not proportionally increase. 10,33 At a given molecular weight, the lower the intrinsic viscosity, the higher the degree of branching. Thus, advanced GPC measuring the viscosity and using that data in mathematical models allows for an evaluation of the degree of branching in the star-shaped polymers.…”

Protected amine-functional initiators for the synthesis of α-amine homo- and heterotelechelic poly(2-ethyl-2-oxazoline)s

“…Functionalities allow conjugation or complexation of cargo such as proteins, 1–3 drugs, 4,5 and genes, 6,7 and targeting and imaging agents. 8,9 They also offer the potential to form complex architectures such as hydrogels, 10 combs, 11 brushes, 12 stars 13,14 and core cross linked micelles. 15 An attractive functionality is the amine group for its ease to form chemical bonds with an abundance of chemical groups such as isothiocyanates, isocyanates, acyl azides, N -hydroxysuccinimide (NHS) esters, sulfonyl chlorides, aldehydes, glyoxals, epoxides, oxiranes, carbonates, aryl halides, imidoesters, carbodiimides, anhydrides, and fluorophenyl esters.…”

Poly(2-oxazoline) with Pendant Hydroxyl Groups via a Silyl Ether-Based Protecting Group

“…The increasing attention of poly­(2-oxazoline)­s (POx) in both biological and industrial applications has led to a plethora of research on this very interesting polymer class. − Numerous literature examples exist regarding the synthesis of POx via cationic ring-opening polymerization (CROP) and are very well summarized in several review articles. − Although the CROP of 2-oxazolines with alkyl side chains can be relatively straightforward in that there are no major interferences from the monomer that can result in chain transfer and/or termination reactions, monomers bearing certain functionalities are not so facile. , In particular, free amines and alcohols as well as acids can have detrimental effects on the pseudoliving nature of the polymerization leading to chain transfer reactions and poorly defined chains. , Therefore, it is important to either have a noninterfering functional group or have a suitable protecting group that will not hinder the polymerization. Alternatively, desirable functional groups can be introduced on the chain end through end-capping. − In general, functional groups on a POx chain can be introduced in three ways: on the α-end by using a functional initiator, on the ω-end through using a functional chain terminator, or by functional side chains. ,− Side chain functionalization can be introduced by either polymerization of a monomer containing the functional group or post-polymerization modification. ,,− …”