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Laser-Responsive Shape Memory Polymer

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Title:
Laser-Responsive Shape Memory Polymer
Creator:
Fei, Rao
Place of Publication:
[Gainesville, Fla.]
Florida
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University of Florida
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english
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1 online resource (27 p.)

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Degree:
Master's ( M.S.)
Degree Grantor:
University of Florida
Degree Disciplines:
Chemical Engineering
Committee Chair:
JIANG,PENG
Committee Co-Chair:
ZIEGLER,KIRK JEREMY

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Subjects / Keywords:
light-responsive -- smp
Chemical Engineering -- Dissertations, Academic -- UF
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bibliography ( marcgt )
theses ( marcgt )
government publication (state, provincial, terriorial, dependent) ( marcgt )
born-digital ( sobekcm )
Electronic Thesis or Dissertation
Chemical Engineering thesis, M.S.

Notes

Abstract:
Shape memory effect has been widely studied for applications in different areas since discovered. However, the development of shape memory polymers has been focusing on the function of whole bulk polymer, regardless of the advantages of faster response and practical uses in smaller scale. Based on a vapor induced surface-reactive shape memory polymer, a laser-responsive spot-reactive shape memory effect is developed, by cooperating the polymer with graphene oxide as the light absorber. The shape memory effect shows a significant color change, as the macroporous structure changes from disordered to highly ordered, driven by the movements of graphene oxide. This laser-responsive localized shape memory effect is proved to be reversible, and could have a promising prospect for its application. ( en )
General Note:
In the series University of Florida Digital Collections.
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Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis:
Thesis (M.S.)--University of Florida, 2017.
Local:
Adviser: JIANG,PENG.
Local:
Co-adviser: ZIEGLER,KIRK JEREMY.
Electronic Access:
RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2018-06-30
Statement of Responsibility:
by Rao Fei.

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Applicable rights reserved.
Embargo Date:
6/30/2018
Classification:
LD1780 2017 ( lcc )

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LASER RESPONSIVE SHAPE MEMORY POLYMER By RAO FEI A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORID A 2017

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2017 R ao Fei

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3 ACKNOWLEDGMENTS I would like to acknowledge my advisor Dr. Peng Jiang, for his advisement and guidance throughout this research. I must also acknowledge the other of my committee, Dr. Kirk J. Ziegler, for his valuable advice to the work. Besides, I would like to th ank Sin Yen Leo for the work on scanning electron microscopy Yifan Zhang for the work on atomic force microscopy and Yongliang Ni and Zhuxiao Gu for their concern and help in lab. Finally, I wo uld like to thank all mentioned above again for the support during my study and experiments, as well as my parents and friends.

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4 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ ............... 3 LIST OF FIGURES ................................ ................................ ................................ ......................... 5 ABSTRACT ................................ ................................ ................................ ................................ ..... 6 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ ........................ 7 1.1 Shape M emory P olymers with N anocomposites ................................ ................................ 7 1.1.1 General Sh ape M emory P olymers ................................ ................................ ............ 7 1.1.2 General M echanism of S hape M emory E ffect ................................ ......................... 7 1.1.3 Light responsive S hape M emory E ffect ................................ ................................ ... 8 1.2 Graphene Oxide ................................ ................................ ................................ .................. 9 1.3 Synthesis ................................ ................................ ................................ ........................... 11 1.3.1 Choice of Shape Memory Polymer ................................ ................................ ........ 11 1.3.2 Synthesis of Graphene Oxide ................................ ................................ ................. 11 1.3.3 Synthesis of 3D H ighly O rdered S ilica S pheres ................................ ..................... 11 2 EXPERIMENTAL SECTION ................................ ................................ ................................ .... 13 2.1 Fabrication of Graphene Oxide ................................ ................................ ........................ 13 2.2 Fabrication o f Laser responsive Shape Memory Polymer Membranes ........................... 13 2.3 Sample Characterization ................................ ................................ ................................ ... 14 2.3.1 Atomic Force Microscopy (AFM) ................................ ................................ .......... 14 2.3.2 Scanning Electron Microscopy (SEM) ................................ ................................ ... 14 2.3.3 Optical Reflection Spectra ................................ ................................ ...................... 14 2.3.4 Laser Recovery ................................ ................................ ................................ ....... 15 3 RESULTS AND DISCUSSION ................................ ................................ ................................ 16 3.1 General Tests ................................ ................................ ................................ .................... 16 3.2 Results of AFM ................................ ................................ ................................ ................. 18 3.2.1 AFM of Graphene Oxide ................................ ................................ ........................ 18 3.2.2 AFM of Shape Memory Polymer Membranes ................................ ....................... 19 3.3 Results of AFM ................................ ................................ ................................ ................. 21 3.4 Results of Optical Reflection Spectra ................................ ................................ ............... 21 4 CONCLUSIONS ................................ ................................ ................................ ......................... 24 LIST OF REFERENCES ................................ ................................ ................................ ............... 25 BIOGRAPHICAL SKETCH ................................ ................................ ................................ ......... 27

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5 LIST OF FIGURES Figure page 1 1 1 Molecular mechanism of the thermally induced shape memory effect. ................................ .. 8 1 2 1 healing ................................ ................................ ............. 10 3 1. Photographs of same polymer membrane . ................................ ................................ ........... 17 3 2 1 Photographs of laser recovery of the polymer membrane. ................................ .................... 18 3 3 1 AFM scan s and height profiles of graphene oxide sheets. ................................ .................... 19 3 4 1 AFM scan of deformed sample surface. ................................ ................................ ................ 20 3 5 1 AFM scan of recovered sample surface. ................................ ................................ ............... 20 3 6 1 Cross sectional SEM image of the sample. ................................ ................................ ........... 21 3 7 1 Normal incidence optical reflection spectra comparing the deformation and recovery from the same shape memory polymer ................................ ................................ ............. 22 3 8 1 Normal incidenc e optical reflection spectra from the same s hape memory polymer recovered for different times. ................................ ................................ ............................. 23

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6 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science LASER RESPONSIVE SHAPE MEMORY POLYMER By Rao F ei December 2017 Chair: Peng Jiang Major: Chemical Engineering Shape memory effect has been widely studied for applications in different areas since dis covered. However, the development of shape memory polymers has been focusing on the function of whole bulk polymer, regardless of the advantages of faster response and practical uses in smaller scale. Based on a vapor induced surface reactive shape memory polymer, a laser responsive spot reactive shape memory effect is developed, by cooperating the polymer with graphene oxide as the light absorber. The shape memory effect shows a significant color change, as the macroporous structure changes from disordered to highly ordered driven by the movements of graphene oxide. This laser responsive localized shape memory effect is proved to be reversible, and could have a promising prospect for its application.

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7 CHAPTER 1 INTRODUCTION 1.1 Shape M emory P olymers with N anocomposites 1.1.1 General Sh ape M emory P olymers Shape memory polymers are an emerging class of active polymers that have the capability to change among their permanent shapes and temporary configurations under external stimulus. 1 3 Since the 1980s, shap e memory polymers have been widely researched. The shape memory effect is a result from a combination of polymer morphology and specific processing, which can be understood as a polymer functionalization. Generally shape memory polymers have the unique adv antages of being lightweight and inexpensive and of having low density, good manufacturability, high shape deformability, and an easily tailorable glass transition temperature compared with shape memory alloys or ceramics. T hey also have some drawbacks, su ch as low deformation stiffness and low recovery stress. Due to their unique properties and development potential, shape memory polymers have become a hot area in various industries and researches. 1,4,5 1.1.2 General M echanism of S hape M emory E ffect The sh ape memory research was in initially founded on the thermally induced dual shape effect. 4 The thermally induced shape memory effect involves polymers whose chain mobility is ver y dependent on temperature ( F ig ure 1 structure which is thermally stable. They can be deformed under some certain methods, but when heated to their glass transition temperatures, as the mobility of chains increases, the polymers tend to

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8 Figure 1 1 1 Molecular mechanism of the thermally induced shape memory effect. 4 Shape memory polymers responding to stimulus other than heat, such as light, electric, magnetic field, and vapor, are then developed, as we human have much higher degr ee of control of them on a pie ce of polymer in most cases. 1 1.1.3 Light responsive S hape M emory E ffect Among the stimulus we have ever discovered, light, of which we can easily control the intensity, wave length, place to shine on, and even polarization co nditions, is one of the best choices. Based on the recovery mechanism, current light responsive shape memory polymers can be categorized into two types. One is known as the photochemical shape memory polymers, which are involved in chemical reactions of t he polymer chains with photons, thus they usually need to interact with light with a specific wavelength (mostly violet or ultraviolet) for the material programming. So far the chemical reactions within the polymer is inconvenient for us to utilize, as a r esult, this type is less reported and applied. 6,7 ,8 The other type is understood as

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9 indirect actuation of the thermal induced shape memory effect. Many published works in this area use infrared or near infrared light source as infrared light has more sig nificant thermal effect. 4, 9 10 This kind of shape memory polymers are usually fabricated by incorporating light absorbers such as carbon nanotubes 9,11 gold nanoparticles 12 and graphene 10 Those light absorbers are considered to absorb energy of light in a range of wave length to increase the temperature of polymer, thus increasing the movements of polymer chains to recovery. In addition to the higher c ontrollability light for indirect heating is considered safer than the direct, electrical, and magnet ic heating. Published works have demonstrated many different ideas on functionalization of the light responsive shape memory polymers, such as differential shrinking 13 and self healing 1 4 However, as the same case of shape memory polymers under other st imulus, present works all focus on the shape change or functionalization of the whole bulk material, wasting the potential of light with localized reactions. Therefore, in this work, my goal is to realize a fast responsive and localized shape memory effect responding to light, which could have promising prospect in fabrications. 1.2 Graphene Oxide Since first published in 2004, graphene, the single layer of sp 2 bonded carbon atoms, has attracted great attention in researches due to its unique mechanical, el ectrical, thermal and optical properties. 1 5 However, some of the properties such as hydrophobicity, along with the expensiveness in fabrication, have always been issues for its applications. On the other hand, as the precursor of graphene, graphene oxide h as much higher solubilities in many common solvents, similar properties, and cheaper price. 1 6 The molecular structure of graphene oxide is very similar to graphene, especially for the edge oxidized ones, and this makes them similar in thermal and optical p roperties. In addition, the oxygenated

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10 functional groups could lower the surface energy, which helps to better disperse in some solvents. 1 8 Among the common used light absorbers (carbon nanotubes, gold nanoparticles, graphene nanosheets), graphene oxide ha s good absorbance crossing all wavelengths of light, meanwhile it is easy to modify the size and the functional groups of graphene oxide. Therefore in this work I choose graphene oxide as the light absorber. In the same case as other light absorbers, the d etailed mechanism of the shape memory effect involving graphene oxide is not strictly studied yet. The role of light absorber has been long considered as either photochemical reactants, or light heat exchanger 4 but recently some work could reveal another physical role for them. In Thakur s publication it was graphene oxide that directly increased the Brow nian movements rather than heat ( F ig ure 1 2). 1 4 Figure 1 2 2 Thakur s mechanism for the self healing, where graphene oxide nanocomposites directly perform work instead of heating. 14

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11 1.3 Synthesis 1.3.1 Choice of Shape Memory Polymer The macroporous photonic crystal shape memory polymer synthesized from ethoxylated (20) trimethylolpropane triacrylate (SR415) and polyethylene glycol (600) diacrylate (SR610) was first reported by Fang in 2015. 3 It had great advantages on fast response speed and cold programming. Further, the functionalization of the polymer only exists at its surface, which means the function could be realized a t a much smaller scale. These aspects are necessary to realize the fast responsive localized shape memory with practical use, so I choose this polymer as well as similar synthesis methods to firstly realize the goal. 1.3.2 Synthesis of Graphene Oxide Due t o the importance of graphene oxide as the precursor of graphene, its synthesis methods have been well established for long. Reacting graphite with strong acid (sulfuric acid) common method to obtain graphene oxide with single atomic lay er. 1 6 ,1 7 In this method, the sp 2 bonding of carbon atoms will not be disrupted, so some electronic properties as well as optical properties will remain similar to graphene. 1.3.3 Synthesis of 3D H ighly O rdered S ilica S pheres The Stber method is a commonly used chemical process to prepare silica nanoparticles with uniform size (less than 5% diameter variation) in material science. During a Stber process, tetraethyl orthosilicate (Si(OEt) 4 ) is hyd rolyzed in the mixture of water and ethanol, then the produced ethoxysilanols condense with each other to form larger molecules, and the diameter of silica particles can be strictly controlled by reactant concentrations, catalysts, and temperature. 19 The c onvective self assembly method technology developed by Jiang 20 could be used to crystalize the synthesized silica spheres into 3D highly ordered structure. In this way, particles

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12 with uniform size could be assembled on the substrate in the hexagonal close st packed structure, and the substrate could then be used as a template to synthesize products with highly ordered porous structure.

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13 CHAPTER 2 EXPERIMENTAL SECTION 2.1 Fabrication of Graphene Oxide Graphene oxide was prepared using Hummers method 1 5 In each batch of synthesis, 0.5 g graphite ( natural, briquetting grade, 100 mesh, Alfa Aesar ) was dispersed in 50 mL concentrated sulfuric acid (A144 212, Fisher Scientific) and stirred for 30 min, then cooled to 0 in an ice bath. 1.2 g KMnO 4 ( Certified ACS Fisher Chemical ) was then slowly added to the mixture, and stirred at 25 for 60 min. The temperature was then elevated to 70 and remained for another hour. After reaction, the mixture was poured into 500 mL water with 3 mL H 2 O 2 ( H325 500, Certified ACS 30%, Fisher Chemical ) The dispersions were centrifuged and washed by equal volume of deionized water for 6 times, and then dried out at 80 at atmospheric pressure. 2.2 Fabrication of Laser responsive Shape Memory Polymer Membranes As is mentioned in the introduction, the synthesis of shape memory polymer is following the method of Fang. 3 First, the synthesis of monodisperse silica microspheres was performed following the Stber method 19 The synthesized silica microspheres were purified in 200 proof etha nol by 6 times of centrifugation and dispersion cycles. The purified silica particles were then assembled on glass microslides using the convecti ve self assembly technology 20 The glass slide with silica colloidal crystal on its surface was covered by anot her microslide, separated by adhesive spacer with thickness of 2.0 mm, to form the template for desired shape memory polymer. Next, the interstitials in between the assembled silica microspheres were filled up with the mixture consisting of ethoxylated (20 ) trimethylolpropane triacrylate (SR415, Sartomer), polyethylene glycol (600) diacrylate (SR610, Sartomer), synthesized graphene oxide, and Darocur 1173 (2 hydroxy 2 methyl 1 phenyl 1 propanone, BASF) as the photoinitiator. The

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14 ratio of SR610 and SR415 was in the range from 1:1 to 6:1, the concentration of photoinitiator was fixed at 1 wt%, and the concentration of graphene oxide was in the range from 0.2% to 1.6%. The monomer mixture was photopolymerized in a pulsed UV curing system (RC 742, Xenon) for tot al ly 24 seconds. Between each run as 4 s, the sample was taken out for cooling for 10 s, and was flipped to the other side facing the lamp. The polymerized membrane was cut off from the glass slide and soaked in a 2 vol% hydrofluoric acid aqueous solution for 5 min and finally rinsed with deionized water. 2.3 Sample Characterization 2.3.1 Atomic Force Microscopy (AFM) Amplitude modulation atomic force microscopy was performed on an MFP 3D AFM (Asylum Research, Inc.) with a PPP NCHR probe (tip radius < 10 nm ) as the sensor. The scan mode was set as AC mode, with scan rate of 1 Hz, scan point of 128, and scan lines of 128, for both shape memory samples and graphene oxide. 2.3.2 Scanning Electron Microscopy (SEM) The scanning electron microscopy images were per formed on an FEI XL 40 FEG SEM, with parameter HV=7.00 kV for deformed sample, and HV=5.00kV for recovered sample. In this case, the magnification was 14000 times, and other parameters were mode=SE, curr=0.18 nA, WD=6.2 mm, and det=TLD for both kind s of sa mples. The sample was cut to expose the boundary between porous and non porous part in cross section, and a gold layer with thickness of 15 nm was sputtered onto the sample for imaging. 2.3.3 Optical Reflection Spectra Normal incidence optical reflection s pectra were obtained on Ocean Optics HR4000 high resolution vis NIR spectrometer with the R600 7 reflection probe and a tungsten halogen light source (LS 1). The maximum reflectivity was obtained from the reflection of an aluminum

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15 sputtered (1000 nm thick) silicon wafer, and zero reflex condition was measured when all the light was reflected out by a wafer set as 45 to the ground. 2.3.4 Laser Recovery The laser recovery of the shape memory polymers were perform ed using a 30mW handheld g reen l aser p ointer ( SKY 30mW handheld 515 nm focusable laser pointer with dual lock) s could be recovered by lasers in other wavelengths as well, but o nly green laser recovered samples are involve d as data in this article.

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16 CHAPTER 3 RESULTS AND DISCUSSION 3.1 General Tests Photographs showing the general looks of the synthesized macroporous shape memo ry polymer membrane are below ( F ig ure 3 1). The polymer can be deformed under water to be come tot ally dark withou t any other external stimulus ( F ig ure 3 3 the polymer could be recovered by vapor of acetone ( F ig ure 3 1b,c), and it seems much shinier n be recovered by irradiation of laser within 2 seconds ( F ig ure 3 1d), which successfully achieves the goal of localized control. The deformation and recovery by laser could be repeated on the same spot of a sample for over 10 times wi thout significant cha nges ( more details in 3.4 Results of O ptical R eflection S pectra). The thermal recovery is however not observed. After heating on a glass substrate in an oven with the temperature from 40 to 110 for 10 min, the shape memory polymers do not show any appare nt change. Temperature higher than 120 would cause the inactivity of the shape memory effect, which means the polymer can no longer be recovered. Similarly, after irradiation on the recovered sample for 10 s, the polymer starts to carbonization. Th ese fac t s strongly suggest that graphene oxide plays a role different from heating the material. A possible explanation could be that the Brownian movements induced by light perform work directly to recover the polymer structure, and this effect is more significa nt in the laser recovery than that induced by heat while they both exist

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17 Figure 3 3 Photographs of same polymer membrane after a) deformation under water. b) & c) e xposing to acetone vapor. d ) recovered by laser irradiation Among all the ratios of SR610 to SR415 from 1:1 to 6:1, the 6:1 ratio gives the best result on shininess of recovery. The ratio of two monomers is then fixed as 6:1, to test the proper concentrations of graphene oxide. In the shape memory effect, graphe ne oxide is supposed to absorb light and transfer the energy for recovery, so the goal is to achieve the highest possible concentration of graphene oxide. The fact is that concentrations higher than 1.3% would make the monomers very difficult to polymerize as most energy of UV is absorbed by graphene oxide. One way to increase the limit is to make thinner membrane by decreasing the thickness of spacer,

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18 but considering the practical uses of the polymer this way is not tried. The concentration is finally fix ed as 1.1% for the spacer thickness of 2.0 mm. Photographs of the laser recovery of a sample with finally fixed ratio and concentration are shown below ( F ig ure 3 2). Figure 3 2 4 Photographs of laser recovery of polymer membran e with ratio of S R610 :SR415=6:1, and 1.1% concentration of graphene oxide a) before the irradiation. b) during the irradiation. c) after the irradiation by the green laser 3.2 Results of AFM 3.2.1 AFM of Graphene Oxide Following graphs from AFM roughly sh ows the thickness and sizes of the graphene oxide sheets ( F ig ure 3 3). The small pieces of graphene oxi de has the size around 100 nm ( F ig ure 3 3c,d), which agrees with the synthesis method. 1 5 2 1 An example of the largest piece of graphene oxide has the siz F ig ure 3 3a,b), which could be a proof of crystallization during the drying of graphene oxide. 3 illustrates (also see 3.3 Results of SEM ), the pore size within my synthesized polymer should be around 280 nm, and the thickness of polymer layer between pores is around 50 nm. According to the results above, some of the graphene oxide may exist in the macroporous part, and some cannot be there.

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19 Figure 3 3 5 a) AFM scan of graphene oxide sheets. b) heig ht profile for the red line in a). c) zoomed in AFM scan. d)height profile for the red line in c) 3.2.2 AFM of Shape Memory Polymer Membranes The AFM of deformed sample ( F ig ure 3 4) shows that the surface of dried polymer is rough. After drying out from w ater, the polymer shows a partly disordered structure at the surface. In contrast, the reco vered surface ( F ig ure 3 5) is smooth er and clearly shows the ordering of the macroporous structur s 3 ,2 2 samples with graphene oxide hav e more defects which can be r ecognized as the dark spots in F ig ure 3 5, and this could be due to the differential heat generated by large pieces of graphene oxide during the polymerization.

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20 Figure 3 4 6 AFM scan of deformed sam ple surface. Figure 3 5 7 AFM scan of recovered sample surface.

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21 3.3 Results of AFM T he cross sectional SEM images ( F ig ure 3 6) strongly support the conclusion from AFM images about surface roughness and ordering of pores. The image from recovered sample having the largest pore shown with diameter of around 270 nm also supports the assumed pore size. The SEM images illustrate that by opening and closing the pores, this shape memory polymer switches its state between deformation an d recovery. This agrees with the assumed mechanism of laser recovery, where rapid movements induced by graphene oxide help the pores open. Figure 3 6 8 Cross sectional SEM image of the a) deformed b) recovered sample 3. 4 Res ults of Optical Reflection Spectra The reflection spectra clearly show apparent optical difference for the deformed and recovere d shape memory polymer ( F ig ure 3 7). While the deformed polymer (blue line) shows reflection just as the baseline (regulated as absolute no reflection at all wavelengths), the laser recovered sample (black line) shows distinct reflection around 550 nm, very similar to the acetone recovered sample (red line) High ordering quality of the pores is again confirmed by the

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22 diffraction p e aks with Fabry Prot fringes 2 3 Compared with Fang s work 3 the blueshift of the main peak could be from the smaller pore size and change of in the ratio of two monomers. Figure 3 7 9 Normal incidence optical reflection spect ra comparing the same shape memory polymer recovered by laser, recovered by acetone and deformed by water. As is mentioned earlier this kind of shape memory effect has good reversibility and durability. F ig ure 3 8 shows the optical reflection spectra from the same sample cyclically recovered by laser and deformed by water. The extensive tests show that the shape memory polymer could be reused for over a hundred times without any apparent difference. However, the localized recovery could cause a tilted surf ace being measured, which would influence the intensity of the main peak as well as its wavelength.

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23 Figure 3 8 10 Normal incidence optical reflection spectra from the same shape memory polymer recovered by laser for 1, 2, 3, 4, 5, and 10 times respectively.

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24 CHAPTER 4 CONCLUSIONS A laser responsive shape memory polymer has been developed. The recovery of the permanent macroporous structure can be triggered by laser with power of 30 mW, and the recovery could be locally triggere d at the surface spot where the laser irradiates The striking color changing is induced by the disorder order transitions of the porous structure, and the work performed by movements of graphene oxide is a main energy source for in the transition of stat es. This laser responsive shape memory polymer is reusable and could play important roles in different technological applications, for instance, light sensor and transducer for remote control.

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25 LIST OF REFERENCES 1 Leng, J., Lan, X., Liu, Y., & Du, S. Shape memory polymers and their composites: stimulus methods and applications. Progress in Materials Science 56 1077 1135 (2011) 2 Meng, H., & Li, G. A review of stimuli responsive shape memory polymer composites. Polymer 54 2199 2221(2013). 3 Fang, Y., Ni, Y., Choi, B., Leo, S. Y., Gao, J., Ge, B., ... & Jiang, P. Chromogenic Photonic Crystals Enabled by Novel Vapor Responsive Shape Memory Polymers. Advanced Materials 27 3696 3704 (2015). 4 Behl, M., & Lendlein, A. Shape memory polymers. Materials t oday 10 20 28 (2007). 5 Liu, Y., Du, H., Liu, L., & Leng, J. Shape memory polymers and their composites in aerospace applications: a review. Smart Materials and Structures 23 023001 (2014). 6 Lendlein, A., Jiang, H., Junger, O., & Langer, R. Light induce d shape memory polymers. Nature 434 879 883 (2005). 7 Li, M. H. et al. Light driven side on nematic elastomer actuators. Advanced Materials 15 569 572 (2003). 8 Yu, Y., & Ikeda, T. Photodeformable polymers: A new kind of promising smart material for micr o and nano applications. Macromolecular Chemistry and Physics 206 1705 1708(2005). 9 Koerner, H., Price, G., Pearce, N. A., Alexander, M., & Vaia, R. A. Remotely actuated polymer nanocomposites stress recovery of carbon nanotube filled thermoplastic elast omers. Nature materials 3 115 120 (2004). 10 Lashgari, S., Karrabi, M., Ghasemi, I., Azizi, H., Messori, M., & Paderni, K. Shape memory nanocomposite of poly (L lactic acid)/graphene nanoplatelets triggered by infrared light and thermal heating. Express P olymer Letters 10 349 (2016). 11 Li, C., Liu, Y., Lo, C. W., & Jiang, H. Reversible white light actuation of carbon nanotube incorporated liquid crystalline elastomer nanocomposites. Soft Matter 7 7511 7516 (2011). 12 Zhang, H., Xia, H., & Zhao, Y Optic ally triggered and spatially controllable shape memory polymer gold nanoparticle composite materials. Journal of Materials Chemistry 22 845 849(2012). 13 Hubbard, A. M., Mailen, R. W., Zikry, M. A., Dickey, M. D., & Genzer, J Controllable curvature from planar polymer sheets in respon se to light. Soft Matter 13 2299 2308(2017).

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26 1 4 Thakur, S., & Karak, N A tough, smart elastomeric bio based hyperbranched polyurethane nanocomposite. New Journal of Chemistry 39 2146 2154 (2015). 1 5 Wang, Y., Shi, Z., Yu, J., Chen, L., Zhu, J., & Hu, Z. Tailoring the characteristics of graphite oxide nanosheets for the production of high performance poly (vinyl alc ohol) composites. Carbon 50 5525 5536 (2012). 1 6 Gambhir, S., Jalili, R., Officer, D. L ., & Wallace, G. G. Chemically converted graphene: scalable chemistries to enable processing and fabri cation. NPG Asia Materials 7 e186 (2015). 1 7 Bepete, G., Anglaret, E., Ortolani, L., Morandi, V., Pnicaud, A., & Drummond, C. Surfactant Free single la yer graphene in water. Nature Chemistry 9 347 (2016) 1 8 Zhu, Y., Murali, S., Cai, W., Li, X., Suk, J. W., Potts, J. R., & Ruoff, R. S. Graphene and graphene oxide: synthesis, properties, and applicat ions. Advanced materials 22 3906 3924 (2010). 19 Stbe r, W., Fink, A., & Bohn, E. Controlled growth of monodisperse silica spheres in the micron size range. Journal of colloid and interface science 26 62 69 (1968). 2 0 Jiang, P., Bertone, J. F., Hwang, K. S., & Colvin, V. L. Single crystal colloidal multilaye rs of controlled thickness. Chemistry of Materials 11 2132 2140 (1999). 2 1 Edwards, R. S., & Coleman, K. S. Graphene synthesis: relationship to applications. Nanoscale 5 38 51 (2013). 2 2 Fang, Y., Leo, S. Y., Ni, Y ., Yu, L., Qi, P., Wang, B., et al & Jia ng, P Optically bistable macroporous photonic crystals enabled by thermoresponsive shape memory polymers. Advanced Optical Materials 3 1509 1516 (2015). 2 3 Jiang, P., Hwang, K. S., Mittleman, D. M., Bertone, J. F., & Colvin, V. L. Template directed prepa ration of macroporous polymers with oriented and crystalline arrays of voids. Journal of the American Chemical Society 121 11630 11637 (1999).

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27 BIOGRAPHICAL SKETCH Rao Fei received his Bachelor of Science in c hemistry from Peking University in 2012 He then began his graduate studies at University of Florida. His research area includes solid state chemistry, shape memory polymer, and nanoscale technologies.