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degradable electroactive polymers: Synthesis, Macromolecular architecture and scaffold design
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electrically conducting polymers induce specific cellular responses at the molecular level. One of the crucial limitations of the use of conducting polymers in tissue engineering is their inability to degrade. The incorporation of conductivity into degradable polymers to obtain materials that are both electroactive and degradable is therefore highly anticipated. Architecture plays an important role in the performance of polymers. To be able to achieve the optimal mechanical, degradation, thermal and biological properties for a particular biomedical application, it is desirable to promote architectural diversity.

 In the first part, by combining the electroactivity of conducting polymers and the degradability of aliphatic polyesters, we have designed and synthesized a series of linear, star-shaped, hyperbranched, and crosslinked degradable and electrically conducting polymers and hydrogels based on polylactide (PLA), polycaprolactone (PCL), and aniline oligomers such as aniline trimer, aniline tetramer, and aniline pentamer. The polymers and hydrogels obtained have good electroactivity, as indicated by their ultraviolet spectra and by cyclic voltammetry. The conductivities of the polymers and hydrogels are tuned by the content of the aniline oligomer and the macromolecular architecture. The hydrophilicity of the polymers was greatly increased after doping the aniline oligomer with acid, which overcomes the hydrophobicity of the PLA and PCL. Thermogravimetric analysis and differential scanning calorimetry studies show that these copolymers and hydrogels have good thermal properties compared to PLA and PCL. The swelling ratios of these hydrogels covered a wide range and were controlled by the degree of crosslinking, the oligoaniline content, and the pH of the surrounding solution.

 In the next part, methods for the facile synthesis of degradable conducting polymers and hydrogels were presented to avoid the multi-step reaction used in the earlier work. We developed a one-pot reaction for the synthesis of degradable conducting polysaccharide hydrogels based on chitosan and aniline tetramer. These hydrogels can form free-standing and flexible conducting films. This overcomes the drawback of polyaniline which could not be easily fabricated into a thin film in common organic solvents. We also presented a universal two-step approach to create degradable conductive diblock or triblock copolymers based on a polyester and aniline tetramer or aniline pentamer by a combination of ring opening polymerization and post-functionalization via an oxidative coupling reaction. The self-assembly behavior of the triblock copolymer consisting of a middle aniline pentamer segment and two bilateral polycaprolactone segments in chloroform as a selective solvent (selective for PCL segment) were also investigated by transmission electron microscopy and dynamic light scattering. The size of the nanoparticles from the assembly of the triblock copolymers depends on the molecular weight of the copolymer and on the aniline pentamer state.

 In the last part, electroactive degradable non-toxic porous tubular scaffolds were fabricated from a polymer blend of hyperbranched degradable conductive copolymer and PCL by a modified solution-casting/particle-leaching technique. The porous structure of the tubular scaffolds was investigated by scanning electron microscope and microcomputed tomography. The hydrophilicity of the blend films was greatly improved by doping with (±)-10-camphorsulfonic acid. The conductivity of the films was tuned by adjusting the ratio of hyperbranched degradable conducting copolymer to PCL. The cytotoxicity test with HaCaT keratinocytes indicated that the materials were non-toxic.

 These degradable electroactive copolymers and hydrogels with different architectures and properties have a great potential for meeting the requirements of biomedical application.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 87 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:55
Keyword [en]
Poly(lactide), poly(ε-caprolactone), ring-opening polymerization, carboxyl-capped aniline trimer, carboxyl-capped aniline pentamer, phenyl amino-capped aniline tetramer, coupling reaction, DCC/DMAP system, degradability, electroactivity, conductivity, macromolecular architecture, chitosan, hydrogel, block copolymer, functionalization, oxidative coupling reaction, self-assembly, toxicity, tubular porous scaffold, neural tissue engineering.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-48171ISBN: 978-91-7501-136-3 (print)OAI: oai:DiVA.org:kth-48171DiVA: diva2:456913
Public defence
2011-12-07, F3, Lindstedsvägen 26, KTH,, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20111123Available from: 2011-11-23 Created: 2011-11-16 Last updated: 2011-11-23Bibliographically approved
List of papers
1. Molecular Achitecture of electroactive and biodegradable copolymers composed of polyactide and carboxyl-capped aniline trimer
Open this publication in new window or tab >>Molecular Achitecture of electroactive and biodegradable copolymers composed of polyactide and carboxyl-capped aniline trimer
2010 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, no 4, 855-863 p.Article in journal (Refereed) Published
Abstract [en]

wo-, four-, and six-armed branched copolymers with electroactive and biodegradable properties were synthesized by coupling reactions between poly(l-lactides) (PLLAs) with different architecture and carboxyl-capped aniline trimer (CCAT). The aniline oligomer CCAT was prepared from amino-capped aniline trimer and succinic anhydride. FT-IR, NMR, and SEC analyses confirmed the structure of the branched copolymers. UV−vis spectra and cyclic voltammetry of CCAT and copolymer solution showed good electroactive properties, similar to those of polyaniline. The water contact angle of the PLLAs was the highest, followed by the undoped copolymer and the doped copolymers. The values of doped four-armed copolymers were 54−63°. Thermal properties of the polymers were studied by DSC and TGA. The copolymers had better thermal stability than the pure PLLAs, and the Tg between 48−58 °C and Tm between 146−177 °C of the copolymers were lower than those of the pure PLLA counterparts. This kind of electroactive and biodegradable copolymer has a great potential for applications in cardiovascular or neuronal tissue engineering.

National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-12931 (URN)10.1021/bm9011248 (DOI)000276557300004 ()2-s2.0-77950826113 (Scopus ID)
Funder
Swedish Research Council, 2008-5538
Note
QC 20100519Available from: 2010-05-19 Created: 2010-05-19 Last updated: 2017-12-12Bibliographically approved
2. Enhanced Electrical Conductivity by Macromolecular Architecture: Hyperbranched Electroactive and Degradable Block Copolymers Based on Poly(epsilon-caprolactone) and Aniline Pentamer
Open this publication in new window or tab >>Enhanced Electrical Conductivity by Macromolecular Architecture: Hyperbranched Electroactive and Degradable Block Copolymers Based on Poly(epsilon-caprolactone) and Aniline Pentamer
2010 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 43, no 10, 4472-4480 p.Article in journal (Refereed) Published
Abstract [en]

We present macromolecular architecture design as a useful tool to enhance the conductivity of degradable polymers. Linear and hyperbranched copolymers with electrical conductivity and biodegradability were synthesized by an "A(2) + B-n (n=2, 3, 4)" strategy using carboxyl-capped aniline pen tamer (CCAP) and branched poly(epsilon-caprolactone)s (PCLs) by coupling reactions. A more hydrophilic surface and lower crystallinity of the doped emeraldine state of aniline pentamer (EM A P) copolymer was achieved compared with PCLs, and TGA results demonstrated that the CCAP contents in the copolymers were almost the same. The structure of the polymers was characterized by FT-IR. NMR, and SEC. Good electroactivity of the copolymers was confirmed by UV and cyclic voltammetry (CV), and CV showed three pairs of redox peaks. The hyperbranched copolymers had a higher conductivity than the linear ones. It is suggested that the higher conductivity of the hyperbranched copolymer is due to the ordered distribution of peripheral EMAP segments that more easily form a conductive network. Therefore, the conductivity of the polymers is improved and controlled by the macromolecular architecture.

National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-27872 (URN)10.1021/ma100530k (DOI)000277649500010 ()2-s2.0-77952475689 (Scopus ID)
Funder
Swedish Research Council, 2008-5538
Note
QC 20110112Available from: 2011-01-12 Created: 2011-01-03 Last updated: 2017-12-11Bibliographically approved
3. Degradable and Electroactive Hydrogels with Tunable Electrical Conductivity and Swelling Behavior
Open this publication in new window or tab >>Degradable and Electroactive Hydrogels with Tunable Electrical Conductivity and Swelling Behavior
2011 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 23, no 5, 1254-1262 p.Article in journal (Refereed) Published
Abstract [en]

Degradable electrically conducting hydrogels (DECHs), which combine the unique properties of degradable polymers and electrically conducting hydrogels, were synthesized by introducing biodegradable segments into conductive hydrogels. These DECHs were obtained by joining together the photopolymerized macromer acrylated poly(D,L-lactide)-poly(ethylene glycol)-poly(D,L-lactide) (AC-PLA-PEG-PLA-AC), glycidyl methacrylate (GMA), ethylene glycol dimethacrylate (EGDMA) network and aniline tetramer (AT) by the coupling reaction between AT and the GMA The electrical conductivity and swelling behavior of these DECHs were tuned by changing the AT content in the hydrogels, the cross-linking degree, and the environmental pH value. The good electroactivity and thermal stability of these hydrogels were demonstrated by UV-vis spectroscopy, cyclic voltammetry, and TGA tests. The chemical structure and morphology of these polymers were characterized by NMR, FT-IR, SEC, and SEM. These hydrogels possessing both degradability and electrical conductivity represent a new class of biomaterial and will lead to various new possibilities in biomedical applications.

Keyword
degradable and conductive hydrogels, electroactive and biodegradable polymers, conductive polymers, tissue engineering
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-31640 (URN)10.1021/cm103498s (DOI)000287767200025 ()2-s2.0-79952159589 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20110321Available from: 2011-03-21 Created: 2011-03-21 Last updated: 2017-12-11Bibliographically approved
4. Versatile Functionalization of Polyester Hydrogels with Electroactive Aniline Oligomers
Open this publication in new window or tab >>Versatile Functionalization of Polyester Hydrogels with Electroactive Aniline Oligomers
2011 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 49, no 9, 2097-2105 p.Article in journal (Refereed) Published
Abstract [en]

Functionalizing aliphatic polyester hydrogels with an aniline oligomer is a means of achieving electrically conductive and degradable hydrogels. To lower the aniline oligomer content while maintaining a high conductivity and to overcome the acidic degradation product from polylactide reported in our previous work, a series of electroactive and degradable hydrogels based on polycaprolactone (PCL) hydrogels and carboxyl-capped aniline pentamer (CCAP) were synthesized by a simple coupling reaction at room temperature. The reaction was carried out between the hydroxyl groups of hydroxyethylmethacrylate in a photopolymerized glycidyl methacrylate (GMA)-functionalized PCL-poly(ethylene glycol)-PCL degradable network and carboxyl group of CCAP, using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as water-condensing agent and 4-dimethylamino-pyridine as catalyst. The electroactivity of the hydrogels was verified by cyclic voltammetry, which showed three pairs of redox peaks. The electrical conductivities and swelling ratios of these hydrogels were controlled by the CCAP content, the poly(ethylene glycol) molecular weight in the macromer, and the crosslinking density of the hydrogels.

Keyword
aniline pentamer, biodegradable hydrogel, biodegradable, conducting hydrogels, conducting polymers, electroactive and degradable polymer, functionalization of polymers, functionalization, hydrogels
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-32616 (URN)10.1002/pola.24643 (DOI)000288966600019 ()2-s2.0-79953061850 (Scopus ID)
Funder
Swedish Research Council, 2008-5538
Note
QC 20110419Available from: 2011-04-19 Created: 2011-04-18 Last updated: 2017-12-11Bibliographically approved
5. Facile Synthesis of Degradable and Electrically Conductive Polysaccharide Hydrogels
Open this publication in new window or tab >>Facile Synthesis of Degradable and Electrically Conductive Polysaccharide Hydrogels
2011 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, no 7, 2601-2609 p.Article in journal (Refereed) Published
Abstract [en]

Degradable and electrically conductive polysaccharide hydrogels (DECPHs) have been synthesized by functionalizing polysaccharide with conductive aniline oligomers. DECPHs based on chitosan (CS), aniline tetramer (AT), and glutaraldehyde were obtained by a facile one-pot reaction by using the amine group of CS and AT under mild conditions, which avoids the multistep reactions and tedious purification involved in the synthesis of degradable conductive hydrogels in our previous work. Interestingly, these one-pot hydrogels possess good film-forming properties, electrical conductivity, and a pH-sensitive swelling behavior. The chemical structure and morphology before and after swelling of the hydrogels were verified by FT-IR, NMR, and SEM. The conductivity of the hydrogels was tuned by adjusting the content of AT. The swelling ratio of the hydrogels was altered by the content of tetraaniline and crosslinker. The hydrogels underwent slow degradation in a buffer solution. The hydrogels obtained by this facile approach provide new possibilities in biomedical applications, for example, biodegradable conductive hydrogels, films, and scaffolds for cardiovascular tissue engineering and controlled drug delivery.

National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-37165 (URN)10.1021/bm200389t (DOI)000292617700021 ()2-s2.0-79960227637 (Scopus ID)
Available from: 2011-08-02 Created: 2011-08-02 Last updated: 2017-12-08Bibliographically approved
6. Universal Two-Step Approach to Degradable and Electroactive Block Copolymers and Networks from Combined Ring-Opening Polymerization and Post-Functionalization via Oxidative Coupling Reactions
Open this publication in new window or tab >>Universal Two-Step Approach to Degradable and Electroactive Block Copolymers and Networks from Combined Ring-Opening Polymerization and Post-Functionalization via Oxidative Coupling Reactions
2011 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 44, no 13, 5227-5236 p.Article in journal (Refereed) Published
Abstract [en]

We present a universal strategy for the facile synthesis of degradable and electroactive block copolymers and organogels (DEBCGs) based on aniline oligomers and polyesters in a two-step approach, here exemplified by the preparation of a series of DECBCGs based on aniline tetramer (AT) and poly(e-caprolactone) (PCL). Polyesters with an aniline dimer (AD) segment were first obtained by controlled ring-opening polymerization (ROP) of e-caprolactone initiated by the amine group of AD with or without 2,2-bis(epsilon-caprolactone-4-yl) propane (BCP). The postpolymerization modification via an oxidative coupling reaction between AD and a polyester was then used to form the electroactive segment AT in the copolymers or organogels. The molecular weight and conductivity of the block copolymers and organogels were controlled by the AT content. The chemical structure, electroactivity, and thermal properties of DEBCGs were investigated by FT-IR, NMR, SEC, UV, cyclic voltammetry, TGA, and DSC. Our general strategy for the synthesis of DECBCGs avoids the multiple step reactions and low efficiency involved in previous work.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-37154 (URN)10.1021/ma2009595 (DOI)000292417800022 ()2-s2.0-79959959355 (Scopus ID)
Available from: 2011-08-03 Created: 2011-08-02 Last updated: 2017-12-08Bibliographically approved
7. Simple Route to Size-Tunable Degradable and Electroactive Nanoparticles from the Self-Assembly of Conducting Coil-Rod-Coil Triblock Copolymers
Open this publication in new window or tab >>Simple Route to Size-Tunable Degradable and Electroactive Nanoparticles from the Self-Assembly of Conducting Coil-Rod-Coil Triblock Copolymers
2011 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 23, no 17, 4045-4055 p.Article in journal (Refereed) Published
Abstract [en]

A simple route to size-tunable nanoparticles from the self-assembly of degradable and electrically conductive coil rod coil triblock copolymers based on an aliphatic polyester and conducting species is presented. A series of coil rod coil triblock copolymers consisting of a middle aniline pentamer (AP) segment and two polycaprolactone (PCL) segments were easily synthesized by a combination of a ring-opening polymerization of CL initiated by an aniline dimer (AD) giving AD-PCL and an oxidative coupling reaction between the AD-PCL and p-phenylenediamine. This strategy avoids the multistep reaction used in previous work. The electroactivity of these copolymers was investigated by UV and cyclic voltammetry. The conductivity of the copolymers was dependent on the AP content and the conductivity mechanism of the triblock copolymers is discussed. Interestingly, these triblock copolymers can undergo self-assembly in selective solvent such as CHCl(3) as indicated by NMR and transmission electron microscope (TEM) observations. Dynamic light scattering (DLS) showed that the size of the nanoparticles was dependent on the molecular weight of the copolymers and on the oxidation state of the AP, The morphology of the nanoparticles was studied by TEM and SEM. These triblock copolymers and their size-tunable nanopartides with degradability and electroactivity offer new possibilities in biomedical applications, such as controlled drug delivery, biosensors, and cardiovascular and neural tissue engineering.

Keyword
degradable and electroactive polymers, functionalization, conjugated polymers, amphiphilic, core-shell micelle
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-41288 (URN)10.1021/cm201782v (DOI)000294647700032 ()2-s2.0-80052447054 (Scopus ID)
Note
QC 20110929Available from: 2011-09-29 Created: 2011-09-26 Last updated: 2017-12-08Bibliographically approved
8. Electroactive porous tubular scaffolds with degradability and non-cytotoxicity for neural tissue regeneration
Open this publication in new window or tab >>Electroactive porous tubular scaffolds with degradability and non-cytotoxicity for neural tissue regeneration
Show others...
2011 (English)In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 8, no 1, 144-153 p.Article in journal (Refereed) Published
Abstract [en]

Electroactive degradable porous tubular scaffolds were fabricated from the blends of polycaprolactone and a hyperbranched degradable conducting copolymer at different feed ratios by a solution-casting/salt-leaching method. Scaning electron microscopy (SEM) and microcomputed tomography tests indicated that these scaffolds had homogeneously distributed interconnected pores on the cross-section and surface. The electrical conductivity of films with the same composition as the scaffolds was between 3.4×10(-6) and 3.1×10(-7)Scm(-1), depending on the ratio of hyperbranched degradable conducting copolymer to polycaprolactone. A hydrophilic surface with a contact angle of water about 30° was achieved by doping the films with (±)-10-camphorsulfonic acid. The mechanical properties of the films were investigated by tensile tests, and the morphology of the films was studied by SEM. The scaffolds were subjected to the WST test (a cell proliferation and cytotoxicity assay using water-soluble tetrazolium salts) with HaCaT keratinocyte cells, and the results show that these scaffolds are non-cytotoxic. These degradable electroactive tubular scaffolds are good candidates for neural tissue engineering application.

Keyword
Poly(lactide), poly(ε-caprolactone), ring-opening polymerization, carboxyl-capped aniline trimer, carboxyl-capped aniline pentamer, phenyl amino-capped aniline tetramer, coupling reaction, DCC/DMAP system, degradability, electroactivity, conductivity, macromolecular architecture, chitosan, hydrogel, block copolymer, functionalization, oxidative coupling reaction, self-assembly, toxicity, tubular porous scaffold, neural tissue engineering.
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-48826 (URN)10.1016/j.actbio.2011.09.027 (DOI)000298763500016 ()21985870 (PubMedID)2-s2.0-84855937121 (Scopus ID)
Note
QC 20111123Available from: 2011-11-23 Created: 2011-11-23 Last updated: 2017-12-08Bibliographically approved

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