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2017 Volume 35 Issue 9
2017, 35(9):
Abstract:
2017, 35(9): 1043-1050
doi: 10.1007/s10118-017-1981-y
Abstract:
A novel solvent-sensitive fluorescent actuator with reversibility has been obtained from carbon dots (CDs) inverse opals, which is prepared via infiltrating CDs solution into the interstice of colloidal crystal template, thermal polymerization of CDs materials and removing the colloidal template. The as-prepared CDs inverse opal actuator shows a bending angle of 75° in 10.2 s, bending rate of 7.35 (°)·s-1. In particular, the fluorescence intensity of the films varies during the actuating process. The actuating behavior is attributed to the inhomogeneous swelling/shrinking of the film, which originates from the gradient dewetting by solvent evaporation and hydrogen-bonding interaction between the solvent molecules and oxygen/hydrogen ions of CDs side chain. The CDs inverse opal actuator has the advantages of quick response, good repeatability and strong fluorescence, which gives an important insight into the design and manufacture of novel and advanced solvent-actuators.
A novel solvent-sensitive fluorescent actuator with reversibility has been obtained from carbon dots (CDs) inverse opals, which is prepared via infiltrating CDs solution into the interstice of colloidal crystal template, thermal polymerization of CDs materials and removing the colloidal template. The as-prepared CDs inverse opal actuator shows a bending angle of 75° in 10.2 s, bending rate of 7.35 (°)·s-1. In particular, the fluorescence intensity of the films varies during the actuating process. The actuating behavior is attributed to the inhomogeneous swelling/shrinking of the film, which originates from the gradient dewetting by solvent evaporation and hydrogen-bonding interaction between the solvent molecules and oxygen/hydrogen ions of CDs side chain. The CDs inverse opal actuator has the advantages of quick response, good repeatability and strong fluorescence, which gives an important insight into the design and manufacture of novel and advanced solvent-actuators.
Synthesis of Cyclic Oligo(ethylene adipate)s and Their Melt Polymerization to Poly(ethylene adipate)
2017, 35(9): 1051-1060
doi: 10.1007/s10118-017-1951-4
Abstract:
We present here the first synthesis of cyclic oligo(ethylene adipate)s (COEAs) via pseudo-high dilution condensation reaction of adipoyl chloride with ethylene glycol, and the synthesis of corresponding poly(ethylene adipate) (PEA) via the melt polymerization of COEAs. The structure of COEAs was characterized and proved by 1H-NMR and MALDI-TOF mass measurements. The effects of organic base, reaction temperature and the ratio of adipoyl chloride to ethylene glycol on the yield of COEAs were studied, and the optimum reaction condition was revealed. PEA, a diacid and diol based semi-crystalline green aliphatic polyester, was synthesized by the melt polymerization of COEAs using Ti(n-C4H9O)4 as catalyst and 1, 10-decanediol as initiator at 200℃, which follows the polycondensation-coupling ring-opening polymerization method. Our strategy should be applicable to the synthesis of versatile aliphatic polyesters based on diacid and diol monomers, which have potential applications as biocompatible and biodegradable materials.
We present here the first synthesis of cyclic oligo(ethylene adipate)s (COEAs) via pseudo-high dilution condensation reaction of adipoyl chloride with ethylene glycol, and the synthesis of corresponding poly(ethylene adipate) (PEA) via the melt polymerization of COEAs. The structure of COEAs was characterized and proved by 1H-NMR and MALDI-TOF mass measurements. The effects of organic base, reaction temperature and the ratio of adipoyl chloride to ethylene glycol on the yield of COEAs were studied, and the optimum reaction condition was revealed. PEA, a diacid and diol based semi-crystalline green aliphatic polyester, was synthesized by the melt polymerization of COEAs using Ti(n-C4H9O)4 as catalyst and 1, 10-decanediol as initiator at 200℃, which follows the polycondensation-coupling ring-opening polymerization method. Our strategy should be applicable to the synthesis of versatile aliphatic polyesters based on diacid and diol monomers, which have potential applications as biocompatible and biodegradable materials.
2017, 35(9): 1061-1072
doi: 10.1007/s10118-017-1966-x
Abstract:
Due to the non-crystalline properties of short chain perfluoroalkyl groups, using short chain perfluoroalkyl to stabilize low surface free energy polymers has been a challenging task. In this study, we prepare a series of random copolymers poly(perfluorohexylethyl methacrylate)-co-poly(stearyl acrylate) (P13FMA-co-PSA) and block copolymers poly(perfluorohexylethyl methacrylate)-b-poly(stearyl acrylate) (P13FMA-b-PSA), and systematically investigate the effects of the sequence structure and the content of 13FMA of the fluorinated copolymers on surface free energy and surface reorganization. Static/dynamic contact angle goniometry and water/oil repellency analyses demonstrate that the random polymer P13FMA-co-PSA could not achieve low surface free energy and low surface reorganization at the same time. In contrast, for the block copolymer P13FMA-b-PSA, both low surface free energy and low surface reorganization are acquired simultaneously. The results of X-ray photoelectron spectroscopy (XPS), dynamic contact angle goniometry and differential scanning calorimetry (DSC) reveal the above-mentioned properties. The consecutive 13FMA segments improve the surface fluorine density, while the consecutive SA chains enhance the crystallinity of the SA segments, and further hinder the surface reorganization of the perfluoroalkyl groups. Therefore, P13FMA-b-PSA exhibits a higher utilization efficiency of fluorine atoms and a better structural stability than P13FMA-co-PSA.
Due to the non-crystalline properties of short chain perfluoroalkyl groups, using short chain perfluoroalkyl to stabilize low surface free energy polymers has been a challenging task. In this study, we prepare a series of random copolymers poly(perfluorohexylethyl methacrylate)-co-poly(stearyl acrylate) (P13FMA-co-PSA) and block copolymers poly(perfluorohexylethyl methacrylate)-b-poly(stearyl acrylate) (P13FMA-b-PSA), and systematically investigate the effects of the sequence structure and the content of 13FMA of the fluorinated copolymers on surface free energy and surface reorganization. Static/dynamic contact angle goniometry and water/oil repellency analyses demonstrate that the random polymer P13FMA-co-PSA could not achieve low surface free energy and low surface reorganization at the same time. In contrast, for the block copolymer P13FMA-b-PSA, both low surface free energy and low surface reorganization are acquired simultaneously. The results of X-ray photoelectron spectroscopy (XPS), dynamic contact angle goniometry and differential scanning calorimetry (DSC) reveal the above-mentioned properties. The consecutive 13FMA segments improve the surface fluorine density, while the consecutive SA chains enhance the crystallinity of the SA segments, and further hinder the surface reorganization of the perfluoroalkyl groups. Therefore, P13FMA-b-PSA exhibits a higher utilization efficiency of fluorine atoms and a better structural stability than P13FMA-co-PSA.
2017, 35(9): 1073-1085
doi: 10.1007/s10118-017-1967-9
Abstract:
A series of novel low band gap donor-acceptor (D-A) type organic co-polymers (BT-F-TPA, BT-CZ-TPA and BT-SI-TPA) consisting of electron-deficient acceptor blocks both in main chains (M1) and at the pendant (M2) were polymerized with different electron rich donor (M3-M5) blocks, i.e., 9, 9-dihexyl-9H-fluorene, N-alkyl-2, 7-carbazole, and 2, 6-dithinosilole, respectively, via Suzuki method. These polymers exhibited relatively low band gaps (1.65-1.88 eV) and broad absorption ranges (680-740 nm). Bulk heterojunction (BHJ) solar cells incorporating these polymers as electron donors, blended with[6, 6]-phenyl-C61-butyric acid methyl ester (PC61BM) or[6, 6]-phenyl-C71-butyric acid methyl ester (PC71BM) as electron-acceptors in different weight ratios were fabricated and tested under 100 mW/cm2 of AM 1.5 with white-light illumination. The photovoltaic device containing donor BT-SI-TPA and acceptor PC71BM in 1:2 weight ratio showed the best power conversion efficiency (PCE) value of 1.88%, with open circuit voltage (Voc)=0.75 V, short circuit current density (Jsc)=7.60 mA/cm2, and fill factor (FF)=33.0%.
A series of novel low band gap donor-acceptor (D-A) type organic co-polymers (BT-F-TPA, BT-CZ-TPA and BT-SI-TPA) consisting of electron-deficient acceptor blocks both in main chains (M1) and at the pendant (M2) were polymerized with different electron rich donor (M3-M5) blocks, i.e., 9, 9-dihexyl-9H-fluorene, N-alkyl-2, 7-carbazole, and 2, 6-dithinosilole, respectively, via Suzuki method. These polymers exhibited relatively low band gaps (1.65-1.88 eV) and broad absorption ranges (680-740 nm). Bulk heterojunction (BHJ) solar cells incorporating these polymers as electron donors, blended with[6, 6]-phenyl-C61-butyric acid methyl ester (PC61BM) or[6, 6]-phenyl-C71-butyric acid methyl ester (PC71BM) as electron-acceptors in different weight ratios were fabricated and tested under 100 mW/cm2 of AM 1.5 with white-light illumination. The photovoltaic device containing donor BT-SI-TPA and acceptor PC71BM in 1:2 weight ratio showed the best power conversion efficiency (PCE) value of 1.88%, with open circuit voltage (Voc)=0.75 V, short circuit current density (Jsc)=7.60 mA/cm2, and fill factor (FF)=33.0%.
2017, 35(9): 1086-1096
doi: 10.1007/s10118-017-1964-z
Abstract:
Poly(propylene carbonate) (PPC), the copolymerization product of carbon dioxide and propylene oxide, was chlorinated for the first time in our laboratory. Nuclear magnetic resonance (NMR) spectroscopy and ion chromatography test showed that chlorine atoms were successfully introduced onto the polymer chains of PPC. We named this newborn polymer material as chlorinated poly(propylene carbonate) (CPPC). It is worth noting that the reaction conditions of the chlorination of PPC were quite mild, which could be easily and simply realized at industrial level. What is more important is that CPPC possessed many more distinguished properties in solubility, wettability, adhesiveness, and gas barrier compared with PPC. For example, the bonding strength of CPPC as thermal adhesive is nearly four times higher than that of PPC for wood, stainless steel and glass. The oxygen permeability coefficient of CPPC exhibits a decrease of 33% compared with that of PPC. Moreover, CPPC is quite stable in air, whereas it could be well biodegraded in soil compared with PPC. These results indicated that CPPC could be widely used in the fields of coating, adhesive, barrier materials and so on, which could greatly promote the development of PPC industry.
Poly(propylene carbonate) (PPC), the copolymerization product of carbon dioxide and propylene oxide, was chlorinated for the first time in our laboratory. Nuclear magnetic resonance (NMR) spectroscopy and ion chromatography test showed that chlorine atoms were successfully introduced onto the polymer chains of PPC. We named this newborn polymer material as chlorinated poly(propylene carbonate) (CPPC). It is worth noting that the reaction conditions of the chlorination of PPC were quite mild, which could be easily and simply realized at industrial level. What is more important is that CPPC possessed many more distinguished properties in solubility, wettability, adhesiveness, and gas barrier compared with PPC. For example, the bonding strength of CPPC as thermal adhesive is nearly four times higher than that of PPC for wood, stainless steel and glass. The oxygen permeability coefficient of CPPC exhibits a decrease of 33% compared with that of PPC. Moreover, CPPC is quite stable in air, whereas it could be well biodegraded in soil compared with PPC. These results indicated that CPPC could be widely used in the fields of coating, adhesive, barrier materials and so on, which could greatly promote the development of PPC industry.
2017, 35(9): 1097-1109
doi: 10.1007/s10118-017-1961-2
Abstract:
A diquinoxalinopyrene (DQP) derivative and the corresponding oligomers (PDQPs) with Mn of ca. 3300, 4200, 5600, and 7300 have been synthesized. It is found that the band gaps and highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels between DQP and its homopolymers only have a slight difference, implying a limited conjugation extension achieved from unimer to heptamer. The DFT calculation is in accordance with the experimental results. It reveals that the nodal planes are across the 2, 11-positions in the LUMO and/or HOMO of DQP, dimer and trimer, which can be used to explain this special phenomenon.
A diquinoxalinopyrene (DQP) derivative and the corresponding oligomers (PDQPs) with Mn of ca. 3300, 4200, 5600, and 7300 have been synthesized. It is found that the band gaps and highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels between DQP and its homopolymers only have a slight difference, implying a limited conjugation extension achieved from unimer to heptamer. The DFT calculation is in accordance with the experimental results. It reveals that the nodal planes are across the 2, 11-positions in the LUMO and/or HOMO of DQP, dimer and trimer, which can be used to explain this special phenomenon.
2017, 35(9): 1110-1121
doi: 10.1007/s10118-017-1956-z
Abstract:
Several novel mono(β-enaminoketonato) vanadium complexes bearing constrained cyclic skeleton, including[(C6H5)C6H3C(O)=C(CH2)nCH=N-Ar]VCl2(THF)2 (V3a:n=1, Ar=C6H5; V4a:n=2, Ar=C6H5; V4b:n=2, Ar=C6F5; V4c:n=2, Ar=(C3H7)2C6H3; V5a:n=3, Ar=C6H5), were synthesized and their structure and properties were characterized. The structures of V4c and V5a in solid-state were further confirmed by X-ray crystallographic analysis. Density functional theory (DFT) results indicated that these complexes showed enhanced steric hindrance around the metal center as compared with the acyclic analogues. Upon activation with Et2AlCl and in the presence of ethyl trichloroacetate as a reactivator, all of the complexes exhibited high catalytic activities (107 gPE/(molV·h)) toward ethylene polymerization, and the obtained polymers exhibited unimodal distributions (Mw/Mn=2.0-2.3) even produced at elevated temperatures (70-100℃) and prolonged reaction time. When MAO was employed as a cocatalyst, they only showed moderate catalytic activities (105 gPE/(molV·h)), but the resulting polymers had higher molecular weights (168-241 kg/mol). These vanadium complexes with cyclic skeleton also showed high catalytic activities toward ethylene/norbornene copolymerization. The produced copolymers displayed approximate alternating structure at high in-feed concentration of norbornene. The catalytic capabilities of these complexes could be tuned conveniently by varying ligand structure. Furthermore, the cyclic voltammetry results also proved that these complexes exhibited better redox stabilities than the complexes bearing linear skeleton.
Several novel mono(β-enaminoketonato) vanadium complexes bearing constrained cyclic skeleton, including[(C6H5)C6H3C(O)=C(CH2)nCH=N-Ar]VCl2(THF)2 (V3a:n=1, Ar=C6H5; V4a:n=2, Ar=C6H5; V4b:n=2, Ar=C6F5; V4c:n=2, Ar=(C3H7)2C6H3; V5a:n=3, Ar=C6H5), were synthesized and their structure and properties were characterized. The structures of V4c and V5a in solid-state were further confirmed by X-ray crystallographic analysis. Density functional theory (DFT) results indicated that these complexes showed enhanced steric hindrance around the metal center as compared with the acyclic analogues. Upon activation with Et2AlCl and in the presence of ethyl trichloroacetate as a reactivator, all of the complexes exhibited high catalytic activities (107 gPE/(molV·h)) toward ethylene polymerization, and the obtained polymers exhibited unimodal distributions (Mw/Mn=2.0-2.3) even produced at elevated temperatures (70-100℃) and prolonged reaction time. When MAO was employed as a cocatalyst, they only showed moderate catalytic activities (105 gPE/(molV·h)), but the resulting polymers had higher molecular weights (168-241 kg/mol). These vanadium complexes with cyclic skeleton also showed high catalytic activities toward ethylene/norbornene copolymerization. The produced copolymers displayed approximate alternating structure at high in-feed concentration of norbornene. The catalytic capabilities of these complexes could be tuned conveniently by varying ligand structure. Furthermore, the cyclic voltammetry results also proved that these complexes exhibited better redox stabilities than the complexes bearing linear skeleton.
2017, 35(9): 1122-1131
doi: 10.1007/s10118-017-1965-y
Abstract:
Young's modulus of biaxially oriented polypropylene (BOPP) films prepared with homemade film stretcher was investigated, which can be used to indicate the softness of films. It was found that the modulus of films was decreased by about 69% as the content of polyethylene (PE) added into polypropylene (PP) reached 30%. Also, increasing draw temperature can induce lower stress level during stretching, which may lead to the formation of crystals with low orientation level and thus decreased modulus of films. Based on laboratory study, BOPP films produced on commercial line were studied by differential scanning calorimetry (DSC), wide and small-angle X-ray scattering (WAXS, SAXS) with varying contents of PE. SAXS results show that the crystals are oriented in both machine direction (MD) and transverse direction (TD), and the crystals are more oriented in TD than MD according to the WAXS results for all films. Also, the orientation parameter of crystal along TD increases from 0.68 to 0.83 as the contents of PE increase from 0% to 25%. Meanwhile, the modulus of films in MD declines with increase of PE contents generally, improving the film softness. Orientation of crystals is thus an effective structure parameter to adjust the film softness. The relationship of processing-structure-property is also established.
Young's modulus of biaxially oriented polypropylene (BOPP) films prepared with homemade film stretcher was investigated, which can be used to indicate the softness of films. It was found that the modulus of films was decreased by about 69% as the content of polyethylene (PE) added into polypropylene (PP) reached 30%. Also, increasing draw temperature can induce lower stress level during stretching, which may lead to the formation of crystals with low orientation level and thus decreased modulus of films. Based on laboratory study, BOPP films produced on commercial line were studied by differential scanning calorimetry (DSC), wide and small-angle X-ray scattering (WAXS, SAXS) with varying contents of PE. SAXS results show that the crystals are oriented in both machine direction (MD) and transverse direction (TD), and the crystals are more oriented in TD than MD according to the WAXS results for all films. Also, the orientation parameter of crystal along TD increases from 0.68 to 0.83 as the contents of PE increase from 0% to 25%. Meanwhile, the modulus of films in MD declines with increase of PE contents generally, improving the film softness. Orientation of crystals is thus an effective structure parameter to adjust the film softness. The relationship of processing-structure-property is also established.
2017, 35(9): 1132-1142
doi: 10.1007/s10118-017-1954-1
Abstract:
In this work, completely immiscible polyethylene/polyamide12 (PE/PA12) blends were prepared by high shear extruder. The morphology and mechanical properties of the blends were investigated as a function of rotation speed. It was found that the high shear processing is an effective method to improve the dispersion of the PA12 phase in PE matrix when PA12 contents are 5 wt% and 10 wt%, and the dispersed phase particle size is reduced with the increase of rotation speed from 100 r/min to 500 r/min. However, with further increase of PA12 content to 20 wt%, high shear processing has no effect on the phase morphology of the blends. Accordingly, a largely increased elongation at break and impact strength are observed for PE/PA12/95/5 and PE/PA12/90/10 blends obtained at high rotation speeds but no effect on the property of PE/PA12/80/20. Annealing experiment demonstrated that the obtained phase morphology is not stable thus compatibilizer should be introduced in the future work. This work could provide a guideline for the application of high shear processing in the preparation of polymer blends with huge polarity difference.
In this work, completely immiscible polyethylene/polyamide12 (PE/PA12) blends were prepared by high shear extruder. The morphology and mechanical properties of the blends were investigated as a function of rotation speed. It was found that the high shear processing is an effective method to improve the dispersion of the PA12 phase in PE matrix when PA12 contents are 5 wt% and 10 wt%, and the dispersed phase particle size is reduced with the increase of rotation speed from 100 r/min to 500 r/min. However, with further increase of PA12 content to 20 wt%, high shear processing has no effect on the phase morphology of the blends. Accordingly, a largely increased elongation at break and impact strength are observed for PE/PA12/95/5 and PE/PA12/90/10 blends obtained at high rotation speeds but no effect on the property of PE/PA12/80/20. Annealing experiment demonstrated that the obtained phase morphology is not stable thus compatibilizer should be introduced in the future work. This work could provide a guideline for the application of high shear processing in the preparation of polymer blends with huge polarity difference.
2017, 35(9): 1143-1155
doi: 10.1007/s10118-017-1953-2
Abstract:
The effects of maleic anhydride-grafted polypropylene (PP-g-MAH) and maleic anhydride-grafted polyolefin elastomer (POE-g-MAH) on interfacial adhesion properties of the polypropylene/magnesium oxysulfate whiskers (PP/MOSw) composites were investigated via mechanical, thermal, ATR-FTIR and rheological tests. Although significant increases in yield strength and Young's modulus were observed in PP-g-MAH treated composites, a sharp decline in these properties was observed in POE-g-MAH treated composites. ATR-FTIR results indicated that esterification occurred between the hydroxyl groups of MOSw and the carbonyls of anhydrides of both compatibilizers but POE-g-MAH was still incompatible with the PP matrix, as verified by the presence of shoulder peaks in DTG curves and numerous voids in SEM micrographs. On the other hand, PP-g-MAH was highly compatible with the PP matrix, as evidenced by the peaks in DTG curves and vague interfaces with wrapped melts on the surface of MOSw. Rheological behaviors also confirmed that introducing PP-g-MAH resulted in a transition from liquid-like to solid-like, which was attributed to the stronger interfacial adhesion between MOSw and the PP matrix. POE-g-MAH treated composites, in contrast to PP-g-MAH, maintained liquid-like rheological behaviors as typical molten polymers. There is likely a MOSw network formed in the PP/15PP-g-MAH/15MOSw composite as suggested by the significant deviation of G' versus G″ plots and the two crossover frequencies observed in plots of tanδ versus frequency.
The effects of maleic anhydride-grafted polypropylene (PP-g-MAH) and maleic anhydride-grafted polyolefin elastomer (POE-g-MAH) on interfacial adhesion properties of the polypropylene/magnesium oxysulfate whiskers (PP/MOSw) composites were investigated via mechanical, thermal, ATR-FTIR and rheological tests. Although significant increases in yield strength and Young's modulus were observed in PP-g-MAH treated composites, a sharp decline in these properties was observed in POE-g-MAH treated composites. ATR-FTIR results indicated that esterification occurred between the hydroxyl groups of MOSw and the carbonyls of anhydrides of both compatibilizers but POE-g-MAH was still incompatible with the PP matrix, as verified by the presence of shoulder peaks in DTG curves and numerous voids in SEM micrographs. On the other hand, PP-g-MAH was highly compatible with the PP matrix, as evidenced by the peaks in DTG curves and vague interfaces with wrapped melts on the surface of MOSw. Rheological behaviors also confirmed that introducing PP-g-MAH resulted in a transition from liquid-like to solid-like, which was attributed to the stronger interfacial adhesion between MOSw and the PP matrix. POE-g-MAH treated composites, in contrast to PP-g-MAH, maintained liquid-like rheological behaviors as typical molten polymers. There is likely a MOSw network formed in the PP/15PP-g-MAH/15MOSw composite as suggested by the significant deviation of G' versus G″ plots and the two crossover frequencies observed in plots of tanδ versus frequency.
2017, 35(9): 1156-1164
doi: 10.1007/s10118-017-1969-7
Abstract:
One-pot polymerization with macroinitiator is supposed to be a robust, facile way to synthesize well-defined core-shell nanoparticles with fixed shell thickness. To testify this, we investigated the temperature-depending morphology evolution of polystyrene (PS) core/poly(N-isopropylacrylamide) (PNIPAM) shell microgel synthesized by one-pot polymerization with PNIPAM-RAFT as macroinitiator in dimethylformamide (DMF) by transmission electron microscopy (TEM), dynamic/static light scattering (DLS/SLS) and small angle neutron scattering (SANS). It is revealed that the microgel has a core-shell structure, i.e., the core is made of pure PS, but the shell is composed of both PNIPAM-RAFT macroinitiator and crosslinked PS. In fact, there are 92.0 wt% D2O, 6.7 wt% PNIPAM and 1.3 wt% PS in the shell in its aqueous dispersion at 21℃; therefore, its shell thickness is much larger than the extended chain length of the macroinitiator as revealed by both SANS and DLS observations. Competitive growth of styrene, divinylbenzene and PNIPAM macroinitiator as well as possible chain transfer from amine proton of PNIPAM side chain may lead to the larger shell thickness, compared with the extended chain length of the macroinitiator. Our work can shed light on the real morphology control in one-pot polymerization.
One-pot polymerization with macroinitiator is supposed to be a robust, facile way to synthesize well-defined core-shell nanoparticles with fixed shell thickness. To testify this, we investigated the temperature-depending morphology evolution of polystyrene (PS) core/poly(N-isopropylacrylamide) (PNIPAM) shell microgel synthesized by one-pot polymerization with PNIPAM-RAFT as macroinitiator in dimethylformamide (DMF) by transmission electron microscopy (TEM), dynamic/static light scattering (DLS/SLS) and small angle neutron scattering (SANS). It is revealed that the microgel has a core-shell structure, i.e., the core is made of pure PS, but the shell is composed of both PNIPAM-RAFT macroinitiator and crosslinked PS. In fact, there are 92.0 wt% D2O, 6.7 wt% PNIPAM and 1.3 wt% PS in the shell in its aqueous dispersion at 21℃; therefore, its shell thickness is much larger than the extended chain length of the macroinitiator as revealed by both SANS and DLS observations. Competitive growth of styrene, divinylbenzene and PNIPAM macroinitiator as well as possible chain transfer from amine proton of PNIPAM side chain may lead to the larger shell thickness, compared with the extended chain length of the macroinitiator. Our work can shed light on the real morphology control in one-pot polymerization.
