Increasing the hydrophilicity of star‐shaped amphiphilic co‐networks by using of PEG and dendritic s‐PCL cross‐linkers

Abstract

New hyperbranched hydrophobic cross‐linkers with peripheral azide groups were synthesized as follows: First, star‐shaped polycaprolactones (sPCL) were synthesized by ring‐opening polymerization of caprolactone in the presence of pentaerythritol and tin (II) octoate. In the next step, sequential acrylation, Micheal addition, tosylation, and azidation by acryloyl chloride, diethanol amine, tosyl chloride, and sodium azide were respectively exploited to synthesize azide‐functionalized hyperbranched star‐shaped polycaprolactones which were named sPCL‐acrylate‐diethanolamine‐azide (sPCL‐AC‐DEA‐N3) and sPCL‐acrylate‐diethanolamine‐acrylate‐diethanolamine‐azide (sPCL‐AC‐DEA‐AC‐N3). All steps were thoroughly characterized by FT‐IR and 1H NMR spectroscopy. The GPC analysis showed that the molecular weight of sPCL increased after two azide functionalizations. Amphiphilic hydrogels based on sPCL‐AC‐DEA‐N3 (Mn = 8130 g/mol) and sPCL‐AC‐DEA‐AC‐N3 (Mn = 10112 g/mol) with linear alkyne‐terminated polyethylene glycols (PEG) (Mn = 2000, 4000, and 6000 g/mol) were synthesized through click coupling between azide and alkyne groups. In both hydrogels, the swelling ratio increased by increasing the molecular weight of PEG. The obtained results showed that the branching of the cross‐linker, significantly affected the swelling ratio of hydrogels. For instance, the swelling ratio of sPCL‐AC‐DEA‐AC‐N3 and PEG‐6000 (Q = 900) was higher than sPCL‐AC‐DEA‐N3 and PEG‐6000 (Q = 600). Despite the high cross‐linking density of sPCL‐AC‐DEA‐AC‐DEA‐N3–based hydrogels, the amount of released theophylline was higher than sPCL‐AC‐DEA‐N3–based hydrogels, due to the high content of PEG in these hydrogels.

Amphiphilic Model Networks Based on PEG and PCL Tetra-arm Star Polymers with Complementary Reactivity

“…Focusing on material properties and application but without addressing the network formation process and its influence on network defects, syntheses of highly biocompatible and biodegradable ACNs based on hydrophobic PCL and hydrophilic PEG have been reported several times in the literature. − ACNs with these components are also the subject of the present publication, but with special focus on the process of network formation. With the aim of obtaining networks with highly defined structures, the synthesis was carried out following the tetra-arm approach of Sakai et al In contrast to Sakai, in our method presented here, hydrophobic PCL and hydrophilic PEG tetra-arm stars were linked by the much slower 2-(4-nitrophenyl)-benzoxazinone/amine reaction in organic solvents similar to our earlier synthesis of A 2 -B 4 hybrid networks .…”

Recent advances on synthesis and biomaterials applications of hyperbranched polymers

“…At sufficient length of primary chains, the linear segments could vary the entanglements between branched polymers as the measurements of viscoelastic and thermal properties of hyperbranched polymers have revealed their dependence on DB values (Morikawa & Akagi, 2013). The DB of polymers used in gel network materials can similarly take advantage of this to tune the mechanical properties, including swelling ratios, as seen in hydrogels through manipulating the architecture of branched polymers within the network (Liu, Zhou, Hou, Yang, & Xu, 2019; Zare, Dabbaghi, & Rahmani, 2019). The existence of primary chains in highly branched polymers also introduces the possibility to graft a high density of pendent groups or chains to achieve tunable solution properties (Zhang, Liu, Shao, Miao, & Zhao, 2013).…”

Amphiphilic Model Networks Based on PEG and PCL Tetra-Arm Star Polymers with Complementary Reactivity

“…Focusing on material properties and application, but without addressing the network formation process and its influence on network defects, synthesis of highly biocompatible and biodegradable ACNs based on hydrophobic PCL and hydrophilic PEG have been reported several times in the literature. [40][41][42] ACNs with these components are also subject of the present publication, but, with special focus on the process of network formation. With the aim of obtaining networks with highly defined structures, the synthesis was carried out following the tetra-arm approach of Sakai et al 26 In contrast to Sakai, in our method presented here, hydrophobic PCL and hydrophilic PEG tetraarm stars were linked by the much slower 2-(4-nitrophenyl)-benzoxazinone/amine reaction in organic solvents similar as described earlier for the synthesis of A2-B4 hybrid networks.…”