The Influence of the Hydroxyl Type on Crosslinking Process in Cyclodextrin Based Polyurethane Networks

Abstract

The influence of the hydroxyl groups (OH) type on the polyaddition processes of isocyanates represents a critical approach for the design of multicomponent polyurethane systems. Herein, to prove the effect of hydroxyl nature on both the isocyanate-OH polyaddition reactions and the structure/properties of the resulting networks, two structurally different cyclodextrins in terms of the primary and secondary groups’ ratio were analyzed, namely native β-cyclodextrin (CD) and its derivative esterified to the primary hydroxyl groups with oligolactide chains (CDLA). Thus, polyurethane hydrogels were prepared via the polyaddition of CD or CDLA to isophorone diisocyanate polyethylene glycol-based prepolymers (PEG-(NCO)2). The degradable character of the materials was induced by intercalating oligolactide short sequences into the polymer chains composing the polymer network. In order to establish the influence of the OH type, the synthesis of polyurethane hydrogels was analyzed by a rheological investigation of the overall system reactivity. Materials properties such as swelling behavior, thermal properties and hydrolytic degradation were influenced by the reaction feed. Specifically, the presence of primary OH groups leads to more compact networks with similar water uptake, disregarding the CD content, while the predominance of secondary OH groups together with the presence of oligolactide spacers leads to the fine tuning of the water swelling properties.

Polyethylene Glycol-Isophorone Diisocyanate Polyurethane Prepolymers Tailored Using MALDI MS

“…Therefore, an important issue concerning our study is related to the employed MALDI MS matrix type, among others. For polyurethane analysis, dithranol [ 50 , 52 ], α-cyano-4-hydroxycinnamic acid (α-CHCA) [ 57 , 58 ], 2,5-dihydroxy benzoic acid (DHB) [ 49 , 56 , 59 ], and trans -2-(3-(4- tert -butylphenyl)-2-methyl-2-propenylidene)malononitrile (DCTB) [ 15 ] matrices are most often employed. Recently, DCTB has been proven to be a good matrix for MS analysis of polymers with different structures or molecular weights, including PEG [ 60 ].…”

“…Prepolymerization reactions are very important in the formation of polyurethanes, influencing the properties of the final materials [ 2 ]. One of the most used polyols for obtaining polyurethane prepolymers is polyethylene glycol (PEG) and a considerable number of studies were performed on the reaction between PEG and diisocyanate compounds, as it is a key method for polyurethanes preparation [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ].…”

“…In a recent study, MALDI MS was used to analyze poly(ε-caprolactone)-diol-HMDI prepolymers and also reacted products between prepolymer and sucrose in the early crosslinking stage [ 56 ]. More recently, MALDI MS was successfully employed to investigate the reactive di-functional prepolymer formed from polyethylene glycol (PEG) and IPDI [ 15 ].…”

Polyurethane Degradable Hydrogels Based on Cyclodextrin-Oligocaprolactone Derivatives

“…Usually, polyols are end-capped with IPDI in the first stage followed by a second step that shapes the final material as linear polymers or crosslinked networks. Various characterization techniques are employed for the evaluation of PEG end-capping reaction with IPDI and, lately, MALDI mass spectrometry has emerged as a robust and precise method to monitor the prepolymers [ 13 , 14 ].…”

“…However, other factors may affect the overall reactivity such as the employed solvent and hydrogen bonding among others [ 17 ]. Cyclodextrin-oligolactide oligoesters (CDLA), which are characterized by an increased content of OH-S functions as compared with the native corresponding cyclodextrins, revealed during the dynamic rheology monitoring of the crosslinking with PEG-(NCO) 2 a slower gelation process associated with diminished system reactivity [ 14 ]. Moreover, the insertion of oligoester sequences rendered a biodegradable character to the polyurethane networks proving the involvement of oligolactide OH groups in the crosslinking processes.…”