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. Author manuscript; available in PMC: 2016 Jul 8.
Published in final edited form as: Adv Mater. 2015 May 26;27(26):3947–3952. doi: 10.1002/adma.201501329

Figure 2. Hydroxyl density of SS-PLLA affects the micro-scale structure of microspheres.

Figure 2

a–c) SEM micrographs of microspheres fabricated from a) 4-arm PLLA-100 before (right column) and after (left column) hydroxyl capping. b) 4-arm PLLA-200 before (left column) and after (right column) hydroxyl doubling. c) 16-arm PLLA-100 before (left column) and after (right column) hydroxyl doubling. The hollow-to-non-hollow transition point is 1/300 for 4-arm PLLAs. The hollow-to-spongy transition point for 16-arm PLLAs is 1/50. Scale bars: 100 μm on the top row, 20 μm on the bottom row. d) The structure of microspheres as a function of arm number and arm length. Note: This graph is based on SS-PLLAs without modification. S-MS refers to smooth non-hollow microspheres, NF-MS refers to nanofibrous non-hollow microspheres, S-HMS refers to smooth hollow microspheres, NF-HMS refers to nanofibrous hollow microspheres, S-SMS refers to smooth spongy microspheres, NF-SMS refers to nanofibrous spongy microspheres. As 1/Y and X increase, the transition from MS to HMS is represented by the green line (line on MS), while the transition from HMS to SMS is indicated by the red line (line on SMS). As 1/Y decreases and X increases, the transition from S into NF is represented by the blue line (line on NF).