End-Group Evaluation of HEMA Initiated Poly(ε-caprolactone) Macromonomers via Enzymatic Ring-Opening Polymerization

N Ugur Kaya,Y Avcibasi Guvenilir

doi:10.1155/2015/458756

N Ugur Kaya, Y Avcibasi Guvenilir

Open Access

https://doi.org/10.1155/2015/458756

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Abstract

Poly(ε-caprolactone) (PCL) macromonomers comprising acrylate end-functionality were synthesized via enzymatic ring-opening polymerization (eROP) by utilizing commercially availableCandida antarcticaLipase B (CALB), Novozyme-435. 2-Hydroxyethyl methacrylate (HEMA) was purposed to be the nucleophilic initiator in eROP. The side reactions generated due to the cleavage of ester bonds in HEMA and the growing polymer chains were investigated through altering polymerization period, initiator concentration, temperature, and enzyme concentration.1H NMR evaluations showed that minimum quantities of side reactions were in lower temperatures, initiator concentration, enzyme concentration, and lower monomer conversions. Gel permeation chromatography (GPC) results revealed that lower polydispersity along with number-average molecular weight of end-functionalized PCL macromonomers was obtained depending on higher initiator/monomer ratios, lower temperature (60°C), enzyme concentration (100 mg), and/or polymerization time (2 h). Furthermore, 0.1 HEMA/ε-caprolactone (CL) ratio had higher molecular weight than 0.5 HEMA/CL ratio, while keeping a close value of methacrylate transfer, total methacrylate end-groups, and lower polyester transfer.

Highlights

Polyesters have crucial applications on medical scopes such as tissue engineering and controlled release drug carriers with their intrinsic biocompatible, biodegradable, and nontoxic nature [1]
Macromonomers synthesized at 70∘C, 100 mg Novozyme-435, and 9 mmole/45 mmole Hydroxyethyl methacrylate (HEMA)/CL ratio were obtained at 4 different reaction times (2 h, 3 h, 5 h, and 6 h)
In the first two hours of reaction, approximately the same amount of HEMA was successfully introduced into macromonomers with the sixth hour of reaction; HEMA addition only increased until the third hour and tended to diminish in the following hours

Summary

Introduction

Polyesters have crucial applications on medical scopes such as tissue engineering and controlled release drug carriers with their intrinsic biocompatible, biodegradable, and nontoxic nature [1]. HEMA end-functionalized macromonomers can be used in free-radical acrylic polymerization for the synthesis of comb-like and grafted polymer structures which can be used in drug delivery systems. EROP with “initiator method” enables single-step methacrylate end-functionalized polyester synthesis which is completely free from organometallic catalysts ready to be used for biomedical applications. Srivastava et al [10] reported the anhydrous bulk eROP of CL as Novozyme-435 was the catalyst and HEMA was the initiating nucleophilic alcohol; they obtained comb and grafted polymers from the HEMA endfunctionalized macromonomers via free-radical mechanism. HEMA initiated eROP of CL was performed concerning the side reactions illustrated above It was aimed at revealing the effect of enzyme concentration, temperature, initiator/monomer ratio, reaction time on the end-groups of the macromonomers, and EG formation inside the macromonomer chains

Materials and Methods

Results and Discussion

Conclusions