“滑轮环”拓扑结构增韧聚乳酸及其形状记忆性能和机理探究

doi:10.7503/cjcu20180293

摘要/Abstract

摘要：

通过羟丙基化改性聚轮烷(HPPR)引发L-丙交酯(LLA)开环聚合, 将具有机械互锁特性的“滑轮环”拓扑结构引入到聚乳酸体系中, 制备了高韧度的“滑轮环”聚乳酸基聚氨酯高分子体系(SR-PLAU), 并将其与化学交联的聚乳酸基聚氨酯体系(CC-PLAU), 以及聚乳酸/HPPR原位化学共混体系(PLA/HPPR)进行对比研究. 结果表明“滑轮环”拓扑结构的引入有效地提高了聚乳酸基材料的拉伸性能, 杨氏模量大幅度下降, 当“滑轮环”拓扑结构含量为1%(摩尔分数)时, 材料的断裂伸长率提高了10倍; “滑轮环”拓扑结构的引入赋予材料优异的形状记忆性能, 形状固定率和形状回复率都达到了90%以上. 提出了可能的形状记忆机理, 并利用材料的应力松弛特性对形状记忆机理进行了分析验证. 为材料的增韧改性和新性能研究提供新的理论和思路.

关键词: "滑轮环"拓扑结构, 聚乳酸, 增韧, 原位化学增容共混, 形状记忆性能

Abstract:

To toughen brittle poly(L-lactic acid), the topological slide-ring architecture was introduced by ring opening polymerization of L-lactic acid initiated by hydroxypropyl modified α-CD-based polyrotaxane(HPPR). The thermal properties, mechanical properties, dynamic mechanical properties and shape memory performance of slide-ring polylactic acid based polyurethane(SR-PLAU) and other all samples were investigated. The results show that, the embedding of the slide-ring structure not noly greatly improves the strain at break of polylactic acid, and significantly improves the mechanical properties, but also enables the material good shape memory performance, compared to CC-PLAU and PLA/HPPR. The shape memory mechanism of SR-PLAU was proposed and demonstrated by the stress relaxation characteristics of the materials.

Key words: Topological slide-ring, Polylactide, Toughen, In-situ reactive compatibilization, Shape memory effect

中图分类号:

O631.1⁺1

TrendMD:

吴瑞清, 来婧娟, 潘毅, 邓瑾妮, 郑朝晖, 丁小斌. “滑轮环”拓扑结构增韧聚乳酸及其形状记忆性能和机理探究. 高等学校化学学报, 2018, 39(12): 2797.

WU Ruiqing,LAI Jingjuan,PAN Yi,DENG Jinni,ZHENG Zhaohui,DING Xiaobin. Toughing Polylactide with Topological Slide-ring Structure and Its Shape Memory Effect and Mechanism^†. Chem. J. Chinese Universities, 2018, 39(12): 2797.

图/表 12

Scheme 1 Synthesis route of the chemically cross-linked PLAU

Scheme 2 Synthesis route of HPPR

Scheme 3 Synthesis route of PLLA-based polyurethane with topological slide-ring structure(SR-PLAU)

Table 1 Components and properties of all prepolymers

Polymer	Molar fraction(%)			M_n	$T g a$ /℃	$T m a$ /℃	ΔH_m/(J·g^-1)	$X c b$ (%)
Polymer	n(LLA)/mol	HPPR	BDO	M_n	$T g a$ /℃	$T m a$ /℃	ΔH_m/(J·g^-1)	$X c b$ (%)
PLA-diol	1	0	0.25	44235	53.6	145.9	33.2	35.47
SG-PLA-0.25	1	0.25	0	857361	55.8	158.7	38.9	41.56
SG-PLA-0.5	1	0.5	0	528336	54.9	155.6	35.5	37.93
SG-PLA-1.0	1	1.0	0	353795	53.5	146.5	32.4	34.62
SG-PLA-2.0	1	2.0	0	273156	52.4	144.6	31.9	34.08

Table 1 Components and properties of all prepolymers

Polymer	Molar fraction(%)			M_n	$T g a$ /℃	$T m a$ /℃	ΔH_m/(J·g^-1)	$X c b$ (%)
Polymer	n(LLA)/mol	HPPR	BDO	M_n	$T g a$ /℃	$T m a$ /℃	ΔH_m/(J·g^-1)	$X c b$ (%)
PLA-diol	1	0	0.25	44235	53.6	145.9	33.2	35.47
SG-PLA-0.25	1	0.25	0	857361	55.8	158.7	38.9	41.56
SG-PLA-0.5	1	0.5	0	528336	54.9	155.6	35.5	37.93
SG-PLA-1.0	1	1.0	0	353795	53.5	146.5	32.4	34.62
SG-PLA-2.0	1	2.0	0	273156	52.4	144.6	31.9	34.08

Table 2 Gel content(G) of CC-PLAU, PLA/HPPR blends and SR-PLAUs

Sample	Molar fraction of HPPR(%)	G(%)	Sample	Molar fraction of HPPR(%)	G(%)
CC-PLAU	0	95.3±1.2	SR-PLAU-0.5	0.5	93.3±0.5
PLA/HPPR	2.0	83.2±0.7	SR-PLAU-1.0	1.0	93.3±1.3
SR-PLAU-0.25	0.25	92.6±1.3	SR-PLAU-2.0	2.0	95.4±1.1

Table 3 Thermal properties of CC-PLAU, PLA/HPPR blends and SR-PLAUs

Sample	$T g a$ /℃	$T m a$ /℃	Δ $H m a$ /(J·g^-1)	$X m b$ (%)
CC-PLAU	57.6(62.80^c)	157.4	17.2	18.38
PLA/HPPR-2.0	54.6(75.92^c)	148.6	11.3	12.07
SR-PLAU-0.25	57.7(77.91^c)	156.2	21.2	22.65
SR-PLAU-0.5	56.9(69.06^c)	155.8	19.8	21.15
SR-PLAU-1.0	55.3(66.66^c)	153.4	15.4	16.45
SR-PLAU-2.0	53.7(60.38^c)	152.7	13.9	14.85

Table 3 Thermal properties of CC-PLAU, PLA/HPPR blends and SR-PLAUs

Sample	$T g a$ /℃	$T m a$ /℃	Δ $H m a$ /(J·g^-1)	$X m b$ (%)
CC-PLAU	57.6(62.80^c)	157.4	17.2	18.38
PLA/HPPR-2.0	54.6(75.92^c)	148.6	11.3	12.07
SR-PLAU-0.25	57.7(77.91^c)	156.2	21.2	22.65
SR-PLAU-0.5	56.9(69.06^c)	155.8	19.8	21.15
SR-PLAU-1.0	55.3(66.66^c)	153.4	15.4	16.45
SR-PLAU-2.0	53.7(60.38^c)	152.7	13.9	14.85

Table 4 Mechanical properties of CC-PLAU, PLA/HPPR blends and SR-PLAUs*

Sample	Molar fraction of HPPR(%)	E/MPa	σ_m/MPa	ε_b(%)
CC-PLAU	0	2202±97.7	48±3.2	6.0±0.8
PLA/HPPR-2.0	2.0	1822±119.2	49.3±2.2	14.7±1.1
SR-PLAU-0.25	0.25	2023±168.6	46.6±0.8	10.5±1.2
SR-PLAU-0.5	0.5	1713±142.3	43.9±1.2	17.6±1.7
SR-PLAU-1.0	1.0	1428±87.2	41.6±1.4	35.6±5.7
SR-PLAU-2.0	2.0	1266±53.8	40.2±1.4	60.5±4.5

Fig.1 Thermal-mechanical properties of CC-PLAU, PLA/HPPR and SR-PLAUs

Table 5 Thermal-mechanical properties of CC-PLAU, PLA/HPPR and SR-PLAUs*

Sample	T_g/℃	E'_{(0 ℃)}/MPa	E'_{(80 ℃)}/MPa	E $' (T g - 30 ℃)$ /MPa	E $' (T g + 15 ℃)$ / MPa	E'_R
CC-PLAU	75.92	2349	608.2	1864	407.6	4.57
PLA/HPPR-2.0	65.17	2032	271.7	1654	271.17	6.09
SR-PLAU-0.25	77.91	2229	146.8	1430	123.86	11.55
SR-PLAU-0.5	69.06	1831	133.9	1536	95.7	16.05
SR-PLAU-1.0	66.66	1529	95.7	1232	85.8	14.36
SR-PLAU-2.0	60.38	1292	91.52	1210	63	19.21

Table 5 Thermal-mechanical properties of CC-PLAU, PLA/HPPR and SR-PLAUs*

Sample	T_g/℃	E'_{(0 ℃)}/MPa	E'_{(80 ℃)}/MPa	E $' (T g - 30 ℃)$ /MPa	E $' (T g + 15 ℃)$ / MPa	E'_R
CC-PLAU	75.92	2349	608.2	1864	407.6	4.57
PLA/HPPR-2.0	65.17	2032	271.7	1654	271.17	6.09
SR-PLAU-0.25	77.91	2229	146.8	1430	123.86	11.55
SR-PLAU-0.5	69.06	1831	133.9	1536	95.7	16.05
SR-PLAU-1.0	66.66	1529	95.7	1232	85.8	14.36
SR-PLAU-2.0	60.38	1292	91.52	1210	63	19.21

Table 6 Shape memory properties of CC-PLAU, PLA/HPPR and SR-PLAUs

Sample	ε_n(%)	ε_m(%)	ε_u(%)	ε_p(%)	R_f(%)	R_r(%)
CC-PLAU	0.410	13.14	12.98	4.90	98.74	64.25
PLA/HPPR-2.0	0.400	14.92	14.04	3.29	93.25	79.41
SR-PLAU-0.25	0.325	22.04	21.34	3.33	96.85	85.71
SR-PLAU-0.5	0.358	24.24	23.49	3.00	96.86	88.59
SR-PLAU-1.0	0.178	24.72	23.80	0.78	96.28	97.46
SR-PLAU-2.0	0.162	22.48	21.67	0.64	96.37	97.77

Fig.2 Series of photographs showing the shape memory effect of SR-PLA from temporary spiral shape to permanent straight shape

Table 7 Measured stress relaxation and recovery parameters of the samples*

Sample	Peak relaxation modulus/MPa	Relaxation modulus^a/MPa	Relative relaxation modulus^a(%)	Strain recovery(%)
SR-PLAU-2.0	80.6	75.49	93.71	131.61
PLA/HPPR-2.0	102.7	49.03	47.73	76.01
CC-PLAU	116.7	52.74	45.19	53.03

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