Cross‐Linked Poly(ε‐caprolactone/D,L‐lactide) Copolymers with Elastic Properties

Abstract

Cross‐linked ε‐caprolactone (CL) and D,L‐lactide (DLLA) copolymers with elastic properties were synthesized in three steps. First, the monomers were copolymerized in ring‐opening polymerization to obtain telechelic star‐shaped oligomers with almost completely random monomer distribution. The oligomers were methacrylated with methacrylic anhydride in the second step and cured in a third. Molar CL/DLLA compositions of 30/70, 50/50, 70/30, 90/10, and 100/0 were used to obtain elastic structures with a wide range of properties. The effect of the average length of the copolymer block on the properties of the networks was evaluated with three different co‐initiator contents (0.5, 1.0, and 2.0/100) in the oligomer synthesis. The oligomers were characterized by 13C NMR spectroscopy, size‐exclusion chromatography (SEC), and differential‐scanning calorimetry (DSC). The formation of elastic networks was confirmed by the absence of a flow region in dynamic mechanical analysis (DMA), the increase in Tg in DSC, and the full recovery of the sample dimensions after tensile testing. In addition, gel contents were high and the samples swelled in CH2Cl2. The networks possessed break stresses from 0.7–9.7 MPa with elongations from 80–350%. Networks with 100 or 90% of ε‐caprolactone retained their form in vitro for 12 weeks, but an increase in lactide content made the networks more vulnerable to hydrolysis. Water absorption of the polymers during hydrolysis.magnified imageWater absorption of the polymers during hydrolysis.

Poly(CL/DLLA-b-CL) multiblock copolymers as biodegradable thermoplastic elastomers

“…Typically semi-crystalline poly(L-lactide) and poly(D-lactide) have been used as the hard blocks [9][10][11][12][13][14][15][16][17][18] while amorphous poly(ε-caprolactone) [10][11][12]18], poly(1,3-trimethylene carbonate) [13][14][15] and poly(ethylene oxide) [19] have been often used as soft components in block structured biodegradable TPEs. This study is natural continuum of the earlier work in the field of poly(ester-urethane)s carried by our biopolymer group in Helsinki University of Technology [1,[3][4][5][6][7]. In this study, poly(ε-caprolactone/ D,L-lactide)-b-poly(ε-caprolactone) multiblock copolymers were synthesized to produce biodegradable thermoplastic elastomers.…”

“…Stannous octoate was used as initiator with amount of 0,02 mol%. The reaction procedure is thoroughly discussed in the previous publication of our group by Helminen et al [1].…”

“…One of often favorable characteristic for biomedical materials is elasticity. Elasticity is traditionally achieved by cross-linking techniques and the rubbery properties are resulting from the chemical network structure of thermosets [1]. However, in many biomedical applications, thermoplasticity of an elastomer is a highly favourable property enabling processing, remoulding and even injection of the elastomer in situ.…”

Synthesis, characterization and photopolymerization of vinyl functionalized poly (ε-caprolactone)

“…They degrade mainly by hydrolysis of ester linkages, yield hydroxyl carboxylic acids, which in most cases are ultimately metabolized [2]. The functionalization of oligomers such as ε-caprolactone, with unsaturated groups and subsequent Ultraviolet (UV) curing [3,4] or polymerization [5,6] has been studied. Especially, UV curing is interesting since it usually provides fast, well-controlled and low energy consumption process, capable of forming thin films or predefined patterns, and can be carried out at low temperatures [7].…”

“…It could be more convenient, if the vari-able rate of degradation is obtained by formation of multilayered polymeric coatings, by rapid and wellcontrolled UV curing. Photo-curable functional groups, such as methacrylates have been used most often as unsaturated group attached on precursor oligomers [4][5][6]. Functionalization with coumarin and phenylazide has been reported as well [12,13].…”