梯度共聚物的可控制备及其性能

doi:10.11949/j.issn.0438-1157.20151043

摘要/Abstract

摘要：

梯度共聚物是近年来伴随着活性聚合方法而发展起来的一种新型共聚物,其特点在于单体单元组成沿着分子链方向逐渐变化,链结构界于常见的无规共聚物和嵌段共聚物之间。本文从梯度共聚物的结构特点入手,总结了其可控制备方法、表征手段、物化性质以及应用前景。基于共聚动力学模型控制单体加料速率的半连续活性/可控自由基聚合可实现梯度共聚物的结构定制,基于多步单体进料方式的RAFT乳液聚合则由于其简单和高效将成为梯度共聚物可控制备的重要方法。梯度共聚物的自组装行为和微观聚集态不同于嵌段共聚物,表现出独特的界面活性、热学特性和力学性能,组成梯度结构有望成为调控高分子材料性能的新参数,梯度共聚物有望在乳化剂、相相容剂、阻尼材料、多形状记忆材料等领域得到应用。

关键词: 聚合, 聚合物, 产品工程, 梯度共聚物

Abstract:

Gradient copolymer is a new kind of polymers emerging with the living polymerization techniques. The unique structural feature is the gradual variation of monomeric compositions along the polymeric chains, distinguishing from random and block copolymers. The current paper reviews the preparation techniques, characterization methods, physical properties and potential applications of gradient copolymers. Kinetic model-based monomer feeding policy in controlled/living radical polymerization presents a sophisticated method to precisely synthesize gradient copolymers by design, while many-shot monomer feeding policy in RAFT emulsion polymerization is a facile and efficient technique to tailor-make compositional gradient copolymers. Compared random and block copolymers, gradient copolymers exhibit different self-assembly behaviors in both solution and bulk, resulting in unique interfacial, thermal and mechanical properties. Composition gradient is expected to be a new parameter to finely tune the properties of polymers. Gradient copolymers have shown promising applications in the phase compatibilizers, damping materials and multi-shape memory materials.

Key words: polymerization, polymer, production engineering, gradient copolymer

中图分类号:

TQ325

郭云龙, 罗英武. 梯度共聚物的可控制备及其性能[J]. 化工学报, 2016, 67(1): 218-230.

GUO Yunlong, LUO Yingwu. Controlled synthesis and properties of gradient copolymers[J]. CIESC Journal, 2016, 67(1): 218-230.

参考文献 66

[1]	MATYJASZEWSKI K. Architecturally complex polymers with controlled heterogeneity [J]. Science, 2011, 333 (6046): 1104-1105.
[2]	LUTZ J F, SCHMIDT B V K J, PFEIFER S. Tailored polymer microstructures prepared by atom transfer radical copolymerization of styrene and N-substituted maleimides [J]. Macromolecular Rapid Communications, 2011, 32 (2): 127-135.
[3]	BEGINN U. Gradient copolymers [J]. Colloid and Polymer Science, 2008, 286 (13): 1465-1474.
[4]	ZAREMSKI M Y, KALUGIN D I, GOLUBEV V B. Gradient copolymers: synthesis, structure, and properties [J]. Polymer Science Series A, 2009, 51 (1): 103-122.
[5]	MATYJASZEWSKI K, ZIEGLER M J, AREHART S V, et al. Gradient copolymers by atom transfer radical copolymerization [J]. Journal of Physical Organic Chemistry, 2000, 13 (12): 775-786.
[6]	GEOFFREY H, RALPH M. Block polymers of monovinyl aromatic hydrocarbons and conjugated dienes: US3265765 [P]. 1966.
[7]	SHIN E J, BROWN H A, GONZALEZ S, et al. Zwitterionic copolymerization: synthesis of cyclic gradient copolymers [J]. Angewandte Chemie International Edition, 2011, 50 (28): 6388-6391.
[8]	LUO Y, GUO Y, GAO X, et al. A general approach towards thermoplastic multishape-memory polymers via sequence structure design [J]. Advanced Materials, 2013, 25 (5): 743-748.
[9]	郑超,黄海瑛,何天白. 梯度共聚物研究进展[J]. 应用化学,2014, 31 (11): 1237-1247.ZHENG C, HUANG H Y, HE T B. Research progress in gradient copolymers [J]. Chinese Journal of Applied Chemistry, 2014, 31 (11): 1237-1247.
[10]	WANG J S, MATYJASZEWSKI K. Controlled/"living" radical polymerization. atom transfer radical polymerization in the presence of transition-metal complexes [J]. Journal of the American Chemical Society, 1995, 117(20): 5614-5615.
[11]	CHIEFARI J, CHONG Y K, ERCOLE F, et al. Living free-radical polymerization by reversible addition-fragmentation chain transfer: the RAFT process[J]. Macromolecules, 1998, 31(16): 5559-5562.
[12]	HAWKER C J, BOSMAN A W, HARTH E. New polymer synthesis by nitroxide mediated living radical polymerizations [J]. Chemical Reviews, 2001, 101(12): 3661-3688.
[13]	ODIAN G G. Principles of Polymerization [M]. John Wiley & Sons, 2007.
[14]	BRAUNECKER W A, MATYJASZEWSKI K. Controlled/living radical polymerization: features, developments, and perspectives [J]. Progress in Polymer Science, 2007, 32 (1): 93-146.
[15]	MIN K, LI M, MATYJASZEWSKI K. Preparation of gradient copolymers via ATRP using a simultaneous reverse and normal initiation process (Ⅰ): Spontaneous gradient [J]. Journal of Polymer Science Part A: Polymer Chemistry, 2005, 43 (16): 3616-3622.
[16]	LEFAY C, CCHAREUX B, SAVE M, et al. Amphiphilic gradient poly(styrene-co-acrylic acid) copolymer prepared via nitroxide-mediated solution polymerization. synthesis, characterization in aqueous solution and evaluation as emulsion polymerization stabilizer [J]. Polymer, 2006, 47 (6): 1935-1945.
[17]	GRAY M K, ZHOU H, NGUYEN S T, et al. Synthesis and glass transition behavior of high molecular weight styrene/4-acetoxystyene and styrene/4-hydroxystyrene gradient copolymers made via nitroxide-mediated controlled radical polymerization [J]. Macromolecules, 2004, 37 (15): 5586-5595.
[18]	MIN K, OH J K, MATYJASZEWSKI K. Preparation of gradient copolymers via ATRP in miniemulsion (Ⅱ): Forced gradient [J]. Journal of Polymer Science Part A: Polymer Chemistry, 2007, 45 (8): 1413-1423.
[19]	KARAKY K, PERE E, POUCHAN C, et al. Effect of the synthetic methodology on molecular architecture: from statistical to gradient copolymers [J]. Soft Matter, 2006, 2 (9): 770-778.
[20]	LEE S B, RUSSELL A J, MATYJASZEWSKI K. ATRP synthesis of amphiphilic random, gradient, and block copolymers of 2-(dimethylamino) ethyl methacrylate and n-butyl methacrylate in aqueous media [J]. Biomacromolecules, 2003, 4 (5): 1386-1393.
[21]	JAKUBOWSKI W, JUHARI A, BEST A, et al. Comparison of thermomechanical properties of statistical, gradient and block copolymers of isobornyl acrylate and n-butyl acrylate with various acrylate homopolymers [J]. Polymer, 2008, 49 (6): 1567-1578.
[22]	LI X, LIANG S, WANG W. J, et al. Model-based production of polymer chains having precisely designed end-to-end gradient copolymer composition and chain topology distributions in controlled radical polymerization, a review [J]. Macromolecular Reaction Engineering, 2015, 9(5): 409-417.
[23]	SUN X, LUO Y, WANG R, et al. Semibatch RAFT polymerization for producing ST/BA copolymers with controlled gradient composition profiles [J]. AIChE Journal, 2008, 54 (4): 1073-1087.
[24]	ZHAO Y, LUO Y W, YE C, et al. Model-based design and synthesis of gradient MMA/tBMA copolymers by computer-programmed semibatch atom transfer radical copolymerization [J]. Journal of Polymer Science Part A: Polymer Chemistry, 2009, 47 (1): 69-79.
[25]	ZHOU Y N, LI J J, LUO Z H. Synthesis of gradient copolymers with simultaneously tailor-made chain composition distribution and glass transition temperature by semibatch ATRP: from modeling to application [J]. Journal of Polymer Science Part A: Polymer Chemistry, 2012, 50 (15): 3052-3066.
[26]	ZHOU Y N, LUO Z H, CHEN J H. Theoretical modeling coupled with experimental study on the preparation and characterization comparison of fluorinated copolymers: effect of chain structure on copolymer properties [J]. AIChE Journal, 2013, 59 (8): 3019-3033.
[27]	WANG L, BROADBELT L J. Explicit sequence of styrene/methyl methacrylate gradient copolymers synthesized by forced gradient copolymerization with nitroxide-mediated controlled radical polymerization [J]. Macromolecules, 2009, 42 (20): 7961-7968.
[28]	WANG L, BROADBELT L J. Factors affecting the formation of the monomer sequence along styrene/methyl methacrylate gradient copolymer chains [J]. Macromolecules, 2009, 42 (21): 8118-8128.
[29]	WANG L, BROADBELT L J. Model-based design for preparing styrene/methyl methacrylate structural gradient copolymers [J]. Macromolecular Theory and Simulations, 2011, 20 (3): 191-204.
[30]	LI X, WANG W J, WENG F, et al. Targeting copolymer composition distribution via model-based monomer feeding policy in semibatch RAFT mini-emulsion copolymerization of styrene and butyl acrylate [J]. Industrial & Engineering Chemistry Research, 2014, 53 (18): 7321-7332.
[31]	GUO Y, ZHANG J, XIE P, et al. Tailor-made compositional gradient copolymer by a many-shot RAFT emulsion polymerization method [J]. Polymer Chemistry, 2014, 5 (10): 3363-3371.
[32]	ELSEN A M, LI Y, LI Q, et al. Exploring quality in gradient copolymers [J]. Macromolecular Rapid Communications, 2014, 35 (2): 133-140.
[33]	WANG X G, LUO Y W, LI B G, et al. Ab initio batch emulsion RAFT polymerization of styrene mediated by poly(acrylic acid-b-styrene) trithicicarbonate [J]. Macromolecules, 2009, 42 (17): 6414-6421.
[34]	GUO R, SHI Z, WANG X, et al. Separation and quantification of dead species in styrene RAFT polymerization by gradient polymer elution chromatography [J]. Polymer Chemistry, 2012, 3 (5): 1314-1321.
[35]	LEFEBVRE M D, DE LA CRUZ M O, SHULL K R. Phase segregation in gradient copolymer melts [J]. Macromolecules, 2004, 37 (3): 1118-1123.
[36]	JIANG R, JIN Q, LI B, et al. Phase behavior of gradient copolymers [J]. Macromolecules, 2008, 41 (14): 5457-5465.
[37]	MOK M M, ELLISON C J, TORKELSON J M. Effect of gradient sequencing on copolymer order-disorder transitions: phase behavior of styrene/n-butyl acrylate block and gradient copolymers [J]. Macromolecules, 2011, 44 (15): 6220-6226.
[38]	AKSIMENTIEV A, HOLYST R. Phase behavior of gradient copolymers [J]. The Journal of Chemical Physics, 1999, 111 (5): 2329-2339.
[39]	HASHIMOTO T, TSUKAHARA Y, TACHI K, et al. Structure and properties of tapered block polymers (Ⅳ): “Domain-boundary mixing” and “mixing-in-domain” effects on microdomain morphology and linear dynamic mechanical response [J]. Macromolecules, 1983, 16 (4): 648-657.
[40]	HOOGENBOOM R, THIJS H. M, WOUTERS D, et al. Solvent responsive micelles based on block and gradient copoly (2-oxazoline) s [J]. Macromolecules, 2008, 41 (5): 1581-1583.
[41]	ZHAO Y, LUO Y W, LI B G, et al. pH responsivity and micelle formation of gradient copolymers of methacrylic acid and methyl methacrylate in aqueous solution [J]. Langmuir, 2011, 27 (18): 11306-11315.
[42]	ZHENG C, HUANG H, HE T. Micellization of St/MMA gradient copolymers: a general picture of structural transitions in gradient copolymer micelles [J]. Macromolecular Rapid Communications, 2013, 34 (20): 1654-1661.
[43]	ZHENG C, HUANG H, HE T. Gradient structure-induced temperature responsiveness in styrene/methyl methacrylate gradient copolymers micelles [J]. Macromolecular Rapid Communications, 2014, 35 (3): 309-316.
[44]	OKABE S, SENO K-i, KANAOKA S, et al. Micellization study on block and gradient copolymer aqueous solutions by DLS and SANS [J]. Macromolecules, 2006, 39 (4): 1592-1597.
[45]	GALLOW K C, JHON Y K, GENZER J, et al. Influence of gradient strength and composition profile on the onset of the cloud point transition in hydroxyethyl methacrylate/dimethylaminoethyl methacrylate gradient copolymers [J]. Polymer, 2012, 53 (5): 1131-1137.
[46]	YUAN W, MOK M M, KIM J, et al. Behavior of gradient copolymers at liquid/liquid interfaces [J]. Langmuir, 2009, 26 (5): 3261-3267.
[47]	YUAN W, LAPRADE E J, HENDERSON K J, et al. Formation and mechanical characterization of ionically crosslinked membranes at oil-water interfaces [J]. Soft Matter, 2014, 10 (8): 1142-1150.
[48]	MOK M M, KIM J, WONG C L H, et al. Glass transition breadths and composition profiles of weakly, moderately, and strongly segregating gradient copolymers: experimental results and calculations from self-consistent mean-field theory [J]. Macromolecules, 2009, 42 (20): 7863-7876.
[49]	WONG C L, KIM J, TORKELSON J M. Breadth of glass transition temperature in styrene/acrylic acid block, random, and gradient copolymers: unusual sequence distribution effects [J]. Journal of Polymer Science Part B: Polymer Physics, 2007, 45 (20): 2842-2849.
[50]	MATYJASZEWSKI K, SHIPP D A, MCMURTRY G P, et al. Simple and effective one-pot synthesis of (meth)acrylic block copolymers through atom transfer radical polymerization [J]. Journal of Polymer Science Part A: Polymer Chemistry, 2000, 38 (11): 2023-2031.
[51]	SHINODA H, MATYJASZEWSKI K, OKRASA L, et al. Structural control of poly (methyl methacrylate)-g-poly (dimethylsiloxane) copolymers using controlled radical polymerization: effect of the molecular structure on morphology and mechanical properties [J]. Macromolecules, 2003, 36 (13): 4772-4778.
[52]	HUY T A, ADHIKARI R, WEIDISCH R, et al. Influence of interfacial structure on morphology and deformation behavior of SBS block copolymers [J]. Polymer, 2003, 44 (4): 1237-1245.
[53]	GUO Y, GAO X, LUO Y. Mechanical properties of gradient copolymers of styrene and n-butyl acrylate [J]. Journal of Polymer Science Part B: Polymer Physics, 2015, 53 (12): 860-868.
[54]	LUO Y W, WANG X G, ZHU Y, et al. Polystyrene-block-poly(n-butyl acrylate)-block-polystyrene triblock copolymer thermoplastic elastomer synthesized via RAFT emulsion polymerization [J]. Macromolecules, 2010, 43 (18): 7472-7481.
[55]	TONNAR J, LACROIX-DESMAZES P. One-pot surfactant-free functional latexes by controlled radical polymerization in ab initio emulsion [J]. Soft Matter, 2008, 4 (6): 1255-1260.
[56]	BORISOVA O, BILLON L, ZAREMSKI M, et al. Synthesis and pH-and salinity-controlled self-assembly of novel amphiphilic block-gradient copolymers of styrene and acrylic acid [J]. Soft Matter, 2012, 8 (29): 7649-7659.
[57]	LEFAY C, SAVE M, CHARLEUX B, et al. Miniemulsion polymerization stabilized by a well-defined, amphiphilic gradient poly (styrene-co-acrylic acid) copolymer [J]. Australian Journal of Chemistry, 2006, 59 (8): 544-548.
[58]	HU Z, ZHANG Z. “Gradient” polymer prepared by complex-radical terpolymerization of styrene, maleic anhydride, and N-vinyl pyrrolidone via γ-ray irradiation by use of a RAFT process: synthesis, mechanism, and characterization [J]. Macromolecules, 2006, 39 (4): 1384-1390.
[59]	HU Z, TAO M, ZHANG Z. “Gradient” polymer prepared by complex-radical terpolymerization of styrene, maleic anhydride, and N-vinyl pyrrolidone via gamma ray irradiation by use of a RAFT method (Ⅱ): Used in dispersion polymerization of styrene as a stabilizer [J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007, 302 (1): 307-311.
[60]	KIM J, GRAY M K, ZHOU H, et al. Polymer blend compatibilization by gradient copolymer addition during melt processing: stabilization of dispersed phase to static coarsening [J]. Macromolecules, 2005, 38 (4): 1037-1040.
[61]	KIM J, ZHOU H, NGUYEN S T, et al. Synthesis and application of styrene/4-hydroxystyrene gradient copolymers made by controlled radical polymerization: compatibilization of immiscible polymer blends via hydrogen-bonding effects [J]. Polymer, 2006, 47 (16): 5799-5809.
[62]	PALERMO E F, VAN DER LAAN H L, et al. Impact of π-conjugated gradient sequence copolymers on polymer blend morphology [J]. Polymer Chemistry, 2013, 4 (17): 4606-4611.
[63]	WANG R, LI W, LUO Y, et al. Phase behavior of ternary homopolymer/gradient copolymer blends [J]. Macromolecules, 2009, 42 (6): 2275-2285.
[64]	WANG Y Q, WANG Y, ZHANG H F, et al. A novel approach to prepare a gradient polymer with a wide damping temperature range by in-situ chemical modification of rubber during vulcanization [J]. Macromolecular Rapid Communications, 2006, 27 (14): 1162-1167.
[65]	MOK M M, KIM J, TORKELSON J M. Gradient copolymers with broad glass transition temperature regions: design of purely interphase compositions for damping applications [J]. Journal of Polymer Science Part B: Polymer Physics, 2008, 46 (1): 48-58.
[66]	OGURA Y, TERASHIMA T, SAWAMOTO M. Synchronized tandem catalysis of living radical polymerization and transesterification: methacrylate gradient copolymers with extremely broad glass transition temperature [J]. ACS Macro Letters, 2013, 2 (11): 985-989.> (2): 133-140.
[33]	Wang, X. G.; Luo, Y. W.; Li, B. G.; Zhu, S. P., Ab Initio Batch Emulsion RAFT Polymerization of Styrene Mediated by Poly(acrylic acid-b-styrene) Trithicicarbonate[J]. Macromolecules, 2009, 42 (17): 6414-6421.
[34]	Guo, R.; Shi, Z.; Wang, X.; Dong, A.; Zhang, J., Separation and quantification of dead species in styrene RAFT polymerization by gradient polymer elution chromatography[J]. Polymer Chemistry, 2012, 3 (5): 1314-1321.
[35]	Lefebvre, M. D.; Olvera de La Cruz, M.; Shull, K. R., Phase segregation in gradient copolymer melts[J]. Macromolecules, 2004, 37 (3): 1118-1123.
[36]	Jiang, R.; Jin, Q.; Li, B.; Ding, D.; Wickham, R. A.; Shi, A.-C., Phase behavior of gradient copolymers[J]. Macromolecules, 2008, 41 (14): 5457-5465.
[37]	Mok, M. M.; Ellison, C. J.; Torkelson, J. M., Effect of Gradient Sequencing on Copolymer Order-Disorder Transitions: Phase Behavior of Styrene/n-Butyl Acrylate Block and Gradient Copolymers[J]. Macromolecules, 2011, 44 (15): 6220-6226.
[38]	Aksimentiev, A.; Ho?yst, R., Phase behavior of gradient copolymers[J]. The Journal of chemical physics, 1999, 111 (5): 2329-2339.
[39]	Hashimoto, T.; Tsukahara, Y.; Tachi, K.; Kawai, H., Structure and properties of tapered block polymers. 4."" Domain-boundary mixing"" and"" mixing-in-domain"" effects on microdomain morphology and linear dynamic mechanical response[J]. Macromolecules, 1983, 16 (4): 648-657.
[40]	Hoogenboom, R.; Thijs, H. M.; Wouters, D.; Hoeppener, S.; Schubert, U. S., Solvent responsive micelles based on block and gradient copoly (2-oxazoline) s[J]. Macromolecules, 2008, 41 (5): 1581-1583.
[41]	Zhao, Y.; Luo, Y.-W.; Li, B.-G.; Zhu, S., pH responsivity and micelle formation of gradient copolymers of methacrylic acid and methyl methacrylate in aqueous solution[J]. Langmuir, 2011, 27 (18): 11306-11315.
[42]	Zheng, C.; Huang, H.; He, T., Micellization of St/MMA Gradient Copolymers: A General Picture of Structural Transitions in Gradient Copolymer Micelles[J]. Macromolecular rapid communications, 2013, 34 (20): 1654-1661.
[43]	Zheng, C.; Huang, H.; He, T., Gradient Structure-Induced Temperature Responsiveness in Styrene/Methyl Methacrylate Gradient Copolymers Micelles[J]. Macromolecular rapid communications, 2014, 35 (3): 309-316.
[44]	Okabe, S.; Seno, K.-i.; Kanaoka, S.; Aoshima, S.; Shibayama, M., Micellization study on block and gradient copolymer aqueous solutions by DLS and SANS[J]. Macromolecules, 2006, 39 (4): 1592-1597.
[45]	Gallow, K. C.; Jhon, Y. K.; Genzer, J.; Loo, Y.-L., Influence of gradient strength and composition profile on the onset of the cloud point transition in hydroxyethyl methacrylate/dimethylaminoethyl methacrylate gradient copolymers[J]. Polymer, 2012, 53 (5): 1131-1137.
[46]	Yuan, W.; Mok, M. M.; Kim, J.; Wong, C. L.; Dettmer, C. M.; Nguyen, S. T.; Torkelson, J. M.; Shull, K. R., Behavior of gradient copolymers at liquid/liquid interfaces[J]. Langmuir, 2009, 26 (5): 3261-3267.
[47]	Yuan, W.; Laprade, E. J.; Henderson, K. J.; Shull, K. R., Formation and mechanical characterization of ionically crosslinked membranes at oil-water interfaces[J]. Soft matter, 2014, 10 (8): 1142-1150.
[48]	Mok, M. M.; Kim, J.; Wong, C. L. H.; Marrou, S. R.; Woo, D. J.; Dettmer, C. M.; Nguyen, S. T.; Ellison, C. J.; Shull, K. R.; Torkelson, J. M., Glass Transition Breadths and Composition Profiles of Weakly, Moderately, and Strongly Segregating Gradient Copolymers: Experimental Results and Calculations from Self-Consistent Mean-Field Theory[J]. Macromolecules, 2009, 42 (20): 7863-7876.
[49]	Wong, C. L.; Kim, J.; Torkelson, J. M., Breadth of glass transition temperature in styrene/acrylic acid block, random, and gradient copolymers: Unusual sequence distribution effects[J]. Journal of Polymer Science Part B: Polymer Physics, 2007, 45 (20): 2842-2849.
[50]	Matyjaszewski, K.; Shipp, D. A.; McMurtry, G. P.; Gaynor, S. G.; Pakula, T., Simple and effective one-pot synthesis of (meth)acrylic block copolymers through atom transfer radical polymerization[J]. Journal of Polymer Science Part A: Polymer Chemistry, 2000, 38 (11): 2023-2031.
[51]	Shinoda, H.; Matyjaszewski, K.; Okrasa, L.; Mierzwa, M.; Pakula, T., Structural control of poly (methyl methacrylate)-g-poly (dimethylsiloxane) copolymers using controlled radical polymerization: effect of the molecular structure on morphology and mechanical properties[J]. Macromolecules, 2003, 36 (13): 4772-4778.
[52]	Huy, T. A.; Adhikari, R.; Weidisch, R.; Michler, G. H.; Knoll, K., Influence of interfacial structure on morphology and deformation behavior of SBS block copolymers[J]. Polymer, 2003, 44 (4): 1237-1245.
[53]	Guo, Y.; Gao, X.; Luo, Y., Mechanical properties of gradient copolymers of styrene and n-butyl acrylate[J]. Journal of Polymer Science Part B: Polymer Physics, 2015, 53 (12): 860-868.
[54]	Luo, Y. W.; Wang, X. G.; Zhu, Y.; Li, B. G.; Zhu, S. P., Polystyrene-block-poly(n-butyl acrylate)-block-polystyrene Triblock Copolymer Thermoplastic Elastomer Synthesized via RAFT Emulsion Polymerization[J]. Macromolecules, 2010, 43 (18): 7472-7481.
[55]	Tonnar, J.; Lacroix-Desmazes, P., One-pot surfactant-free functional latexes by controlled radical polymerization in ab initio emulsion[J]. Soft Matter, 2008, 4 (6): 1255-1260.
[56]	Borisova, O.; Billon, L.; Zaremski, M.; Grassl, B.; Bakaeva, Z.; Lapp, A.; Stepanek, P.; Borisov, O., Synthesis and pH-and salinity-controlled self-assembly of novel amphiphilic block-gradient copolymers of styrene and acrylic acid[J]. Soft Matter, 2012, 8 (29): 7649-7659.
[57]	Lefay, C.; Save, M.; Charleux, B.; Magnet, S., Miniemulsion polymerization stabilized by a well-defined, amphiphilic gradient poly (styrene-co-acrylic acid) copolymer[J]. Australian journal of chemistry, 2006, 59 (8): 544-548.
[58]	Hu, Z.; Zhang, Z., “Gradient” polymer prepared by complex-radical terpolymerization of styrene, maleic anhydride, and N-vinyl pyrrolidone via γ-ray irradiation by use of a RAFT process: synthesis, mechanism, and characterization[J]. Macromolecules, 2006, 39 (4): 1384-1390.
[59]	Hu, Z.; Tao, M.; Zhang, Z., “Gradient” polymer prepared by complex-radical terpolymerization of styrene, maleic anhydride, and N-vinyl pyrrolidone via gamma ray irradiation by use of a RAFT method: 2. Used in dispersion polymerization of styrene as a stabilizer[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007, 302 (1): 307-311.
[60]	Kim, J.; Gray, M. K.; Zhou, H.; Nguyen, S. T.; Torkelson, J. M., Polymer blend compatibilization by gradient copolymer addition during melt processing: Stabilization of dispersed phase to static coarsening[J]. Macromolecules, 2005, 38 (4): 1037-1040.
[61]	Kim, J.; Zhou, H.; Nguyen, S. T.; Torkelson, J. M., Synthesis and application of styrene/4-hydroxystyrene gradient copolymers made by controlled radical polymerization: Compatibilization of immiscible polymer blends via hydrogen-bonding effects[J]. Polymer, 2006, 47 (16): 5799-5809.
[62]	Palermo, E. F.; van der Laan, H. L.; McNeil, A. J., Impact of π-conjugated gradient sequence copolymers on polymer blend morphology[J]. Polymer Chemistry, 2013, 4 (17): 4606-4611.
[63]	Wang, R.; Li, W.; Luo, Y.; Li, B.-G.; Shi, A.-C.; Zhu, S., Phase Behavior of Ternary Homopolymer/Gradient Copolymer Blends[J]. Macromolecules, 2009, 42 (6): 2275-2285.
[64]	Wang, Y. Q.; Wang, Y.; Zhang, H. F.; Zhang, L. Q., A Novel Approach to Prepare a Gradient Polymer with a Wide Damping Temperature Range by In-Situ Chemical Modification of Rubber During Vulcanization[J]. Macromolecular rapid communications, 2006, 27 (14): 1162-1167.
[65]	Mok, M. M.; Kim, J.; Torkelson, J. M., Gradient copolymers with broad glass transition temperature regions: Design of purely interphase compositions for damping applications[J]. Journal of Polymer Science Part B: Polymer Physics, 2008, 46 (1): 48-58.
[66]	Ogura, Y.; Terashima, T.; Sawamoto, M., Synchronized tandem catalysis of living radical polymerization and transesterification: methacrylate gradient copolymers with extremely broad glass transition temperature[J]. ACS Macro Letters, 2013, 2 (11): 985-989.