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The nature of polymer grafts and substrate shape on the surface degradation of poly(l-lactide)
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.ORCID iD: 0000-0002-5850-8873
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
2015 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628Article in journal (Refereed) Epub ahead of print
Abstract [en]

Surface grafting of functional polymers is an effective method to alter material properties and degradation behavior. Two different substrate shapes of poly(l-lactide) (PLLA), i.e., films and microparticles, were surface-grafted with hydrophilic monomers, and their surface degradation was monitored. Surface grafting with a hydrophilic and acidic polymer graft [acrylic acid (AA)] induced large alterations in the surface morphology and topography of the films. In contrast, hydrophilic and neutral polymer grafts [acrylamide (AAm)] had no significant effect on the surface degradation behavior, while the PLLA reference and co-monomeric (AA/AAm) polymer-grafted samples exhibited intermediate surface degradation rates. The grafted PAA chains induced a local acidic environment on the surface of the substrates, which in turn catalyzed the surface degradation process. This effect was more pronounced in the films than in the microparticles. Thus, the nature of the grafted chains and substrate geometry were shown to affect the surface degradation behavior of PLLA substrates.

Place, publisher, year, edition, pages
2015.
Keyword [en]
Degradation, Properties and characterization, Surfaces and interfaces
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-173360DOI: 10.1002/app.42736OAI: oai:DiVA.org:kth-173360DiVA: diva2:852808
Note

QP 201509

Available from: 2015-09-10 Created: 2015-09-10 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Modification of polymeric particles via surface grafting for 3D scaffold design
Open this publication in new window or tab >>Modification of polymeric particles via surface grafting for 3D scaffold design
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Surface modification techniques have played important roles in various aspects of modern technology. They have been employed to improve substrates by altering surface physicochemical properties. An ideal surface modifying technique would be a method that is applicable to any kind of materials prepared from a wide range of polymers and that can occur under mild reaction conditions. The work in this thesis has utilized four main concepts: I) the development of a ‘grafting-from’ technique by covalently growing polymer grafts from particle surfaces, II) the presence of steric and electrosteric forces due to long-range repulsive interactions between particles, III) a combined surface grafting and layer-by-layer approach to create polyelectrolyte multilayers (PEMs) on particle surfaces to fabricate strong and functional materials, and IV) the roles of hydrophilic polymer grafts and substrate geometry on surface degradation.

A non-destructive surface grafting technique was developed and applied to polylactide (PLA) particle surfaces. Their successful modification was verified by observed changes to the surface chemistry, morphology and topography of the particles. To quantify the aggregation behavior of grafted and non-grafted particles, force interaction measurements were performed using colloidal probe atomic force microscopy (AFM). Long-range repulsive interactions were observed when symmetric systems, i.e., hydrophilic polymer grafts on two interacting surfaces, and asymmetric system were applied. Electrosteric forces were observed when the symmetric substrates interacted at pH 7.4. When PEMs were alternately assembled on the surface of poly(L-lactide) (PLLA) particles, the grafted surfaces played a dominated role in altering the surface chemistry and morphology of the particles. Three-dimensional scaffolds of surface grafted particle coated with PEMs demonstrated high mechanical performance that agreed well with the mechanical performance of cancellous bone. Nanomaterials were used to functionalize the scaffolds and further influence their physicochemical properties. For example, when magnetic nanoparticles were used to functionalize the scaffolds, a high electrical conductivity was imparted, which is important for bone tissue regeneration. Furthermore, the stability of the surface grafted particles was evaluated in phosphate buffered saline (PBS) solution. The nature of the hydrophilic polymer grafts and the geometry of the PLLA substrates played central roles in altering the surface properties of films and particles. After 10 days of PBS immersion, larger alterations in the surface morphology were observed on the film compared with microparticles grafted with poly(acrylic acid) (PAA). In contrast to the PAA-grafted substrates, the morphology of poly(acrylamide) (PAAm)-grafted substrates was not affected by PBS immersion. Additionally, PAAm-grafted microparticulate substrates encountered surface degradation more rapidly than PAAm-grafted film substrates.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 61 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:48
Keyword
surface grafting, PLA, PLLA, hydrophilic polymers, particles, geometry, steric stabilization, atomic force microscopy (AFM), polyelectrolyte multilayers, 3D scaffold, bone tissue engineering, surface degradation
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-174295 (URN)978-91-7595-686-2 (ISBN)
Public defence
2015-10-29, E3, Osquars backe 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20151002

Available from: 2015-10-02 Created: 2015-10-02 Last updated: 2015-10-02Bibliographically approved

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Odelius, Karin

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