Shape-Memory Polymer Networks from Oligo[(ε-hydroxycaproate)-co-glycolate]dimethacrylates and Butyl Acrylate with Adjustable Hydrolytic Degradation Rate

Abstract

Degradable shape-memory polymer networks intended for biomedical applications were synthesized from oligo-[( -hydroxycaproate)-co-glycolate]dimethacrylates with glycolate contents between 0 and 30 mol % using a photopolymerization process. In addition AB copolymer networks were prepared by adding 60 wt % n-butyl acrylate as comonomer. All synthesized polymer networks are semicrystalline at room temperature. A melting transition T m between 18 and 53°C which can be used as switching transition for the shape-memory effect can be attributed to the crystalline poly( -hydroxycaproate) phase. At temperatures below T m the elastic properties are dominated by these physical cross-links. At temperatures higher than T m the E modulus of the amorphous polymer networks is lowered by up to 2 orders of magnitude, depending on the chemical cross-link density. Copolymer networks based on macrodimethacrylates with a M n of up to 13 500 g‚mol -1 and a maximum glycolate content of 21 mol % show quantitative strain recovery rates in stress-controlled cyclic thermomechanical experiments. Hydrolytic degradation experiments of polymer networks performed in phosphate buffer solution at 37°C show that the degradation rate can be accelerated by increasing the glycolate content and decelerated by the incorporation of n-butyl acrylate. IntroductionMaterials which obtain their functionality after application of a functionalization process such as that described for shapememory polymers can be referred to as functionalized materials. 1 An actual trend in polymer science is the design of materials which show multifunctionality, meaning an unexpected combination of material functionalizations such as the combination of hydrolytic degradability and shape-memory functionality. [2][3][4] The shape-memory effect results from the combination of the polymer architecture with a certain processing and programming technology. The permanent shape of shape-memory polymers is defined by physical or chemical cross-links, while switching segments formed by domains, which are associated with a thermal transition T trans. , enable the fixation of the temporary shape. 1,5 To obtain a defined shape change upon transition of a switching temperature T switch , the temporary shape has to be programmed by application of a thermomechanical treatment. Examples for polymers which combine shape-memory functionality and biodegradability are amorphous polyesterurethane networks based on poly(rac-lactide-co-glycolate) segments having a glass transition temperature T g around 55°C. 5 Poly-[(3-hydroxybutyrate)-co-(3-hydroxyvalerate) (35 mol % 3-hydroxyvalerate) obtained by a biotechnological process showed a shape-memory effect when samples which were programmed by a cold drawing were submitted to temperatures above 75°C. The melting transition used to trigger the shape-memory effect and to define the permanent shape simultaneously ranged from 37 to 115°C. 6 Examples for polymers showing a thermally induced shapememory effect which contain poly( -hydroxycaproate), being con...

In Situ X‐Ray Scattering Studies of Poly(ε‐caprolactone) Networks with Grafted Poly(ethylene glycol) Chains to Investigate Structural Changes during Dual‐ and Triple‐Shape Effect

“…While in AB polymer networks both segments contribute to the overall elasticity of the polymer network, [5] the elasticity in grafted polymer networks is mainly determined by the crosslinking segments. [6,7,10] A versatile synthesis route for SMP networks is based on macrodimethacrylates [11][12][13] obtained from (co)polyesterdiols [14] as starting materials. For the present study a poly(e-caprolactone) network with grafted poly(ethylene glycol) side chains (CLEG) that exhibits two distinct melting transitions T m,PEG (T m,A ) and T m,PCL (T m,B ) was investigated.…”

Amorphous, Elastic AB Copolymer Networks from Acrylates and Poly[(L‐lactide)‐ran‐glycolide]dimethacrylates

“…[8] Shapememory polymers have a high innovation potential as biomaterial, especially for minimally invasive surgery. One basic concept in the development of biodegradable polymer systems with shape-memory properties is based on covalently crosslinked polymer networks, [9][10][11][12] containing switching segments from semi-crystalline poly(e-caprolactone) [10,11,13] or poly[(e-caprolactone)-co-glycolide]. [12] The latter ones enable an accelerated hydrolytic degradation because of the presence of easily hydrolizable ester bonds in the form of glycolate ester bonds.…”

“…One basic concept in the development of biodegradable polymer systems with shape-memory properties is based on covalently crosslinked polymer networks, [9][10][11][12] containing switching segments from semi-crystalline poly(e-caprolactone) [10,11,13] or poly[(e-caprolactone)-co-glycolide]. [12] The latter ones enable an accelerated hydrolytic degradation because of the presence of easily hydrolizable ester bonds in the form of glycolate ester bonds. [12,14] Another approach is the development of AB copolymer photoset networks, which are obtained from poly(e-caprolactone)dimethacrylate with n-butylacrylate or cyclohexylmethacrylate by UV-crosslinking.…”

“…[12] The latter ones enable an accelerated hydrolytic degradation because of the presence of easily hydrolizable ester bonds in the form of glycolate ester bonds. [12,14] Another approach is the development of AB copolymer photoset networks, which are obtained from poly(e-caprolactone)dimethacrylate with n-butylacrylate or cyclohexylmethacrylate by UV-crosslinking. [10,11] These polymer networks showed excellent shape-memory properties and as tested so far good tissue-compatibility, in cell culture and in vivo tests.…”

A smart hollow filament with thermal sensitive internal diameter

“…Also, it may be synthesized with two kinds of long-chain polyols coupled with diisocyanate where one polyol with a higher thermal transition acts as a hard segment and another polyol acts as a soft segment. [1][2][3][4] Smart polyurethanes are not very difficult to synthesize. In addition, some kinds of smart polyurethanes can be processed by using conventional techniques (injection, extrusion, blowing) to desire formats.…”