Polymeric blends comprised of the biodegradable polymer poly-L-lactic acid (PLLA) and polyethylene oxide (PEO) are of considerable interest due to their potential applications as protein drug delivery devices. In such devices, the PEO component will preferentially migrate to the surface, forming a surface enriched PEO region, increasing the biocompatibility of the implanted device, and providing a diffusive hydrophillac layer at the surface, facilitating interactions between the cells of interest and the polymeric biodevice. In addition, the PEO component will enhance the stability of the device by forming micelles around the hydrophillac protein components within the biodevice. This surface segregated region is extremely important and hence needs to be studied in greater detail. In the current work, Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) employing an SF5+ primary ion source was utilized to obtain a series of in-depth profiles from PLLA/Pluronic -P104 (Polyethylene oxide-co-propylene oxide triblock copolymer [PEO-PPO-PEO]) blends of varying compositions in attempts to study this surface segregated PEO region in detail. These profiles represent our first successful attempt to directly monitor the surface segregation that occurs in a polymeric blend. This success can be attributed to the utilization of a polyatomic primary ion beam source (SF5+), which has allowed us to obtain in-depth information from polymeric biomaterials for the first time. These profiles are consistent with theoretical models describing the surface segregated region in polymeric blends and copolymer systems. In each profile, there was a surface enriched Pluronic -P104 region, followed by a P104 depletion layer, and finally a constant composition bulk region. These results were consistent over a range of concentrations (1-25%). The depth profiles obtained using cluster SIMS were compared to information obtained using X-ray Photoelectron Spectroscopy (XPS). The results demonstrate that with cluster primary ion bombardment, we are for the first time able to directly monitor the polymeric composition as a function of depth within certain multicomponent polymer blends.
Citation: Analytical Chemistry
Volume: 77 No. 11
Pub Type: Journals
depth profile, P104, pluronic, poly (lactic acid), polyethylene glycol (PEG), polyethylene oxide, polymer blends, polypropylene oxide, TOF-SIMS