Polymerized Microgel Colloidal Crystals Photonic Hydrogels with Tunable Band Gaps and Fast Response Rates
聚合微凝胶胶体晶体光子水凝胶具有可调谐带隙和快速响应速率

Experimental details

Materials

N-Isopropylacrylamide (NIPAM) was purchased from Tokyo Chemical Industry Co. 2-Hydroxyethyl methacrylate (HEMA) was purchased from ACROS. Sodium dodecy sulfate (SDS) was purchased from Sigma-Aldrich. N,N’methylenebis(acrylamide) (BIS) and 2,2-diethoxyacetophenone (DEAP) were purchased from Alfa Asear. Acrylic acid (AAc), potassium persulfate (KPS), sodium chloride (NaCl), N-(3-Dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDC) were purchased from local providers. NIPAM was purified by recrystallization from hexane/acetone mixture and dried in a vacuum. AAc and HEMA were distilled under reduced pressure. Other reagents were used as received.
N-异丙基丙烯酰胺（NIPAM）购自Tokyo Chemical Industry Co. 2-羟乙基甲基丙烯酸酯（HEMA）购自ACROS。 十二烷基硫酸（SDS）购自Sigma-Aldrich。 N，N'-亚甲基双（丙烯酰胺）（BIS）和2,2-二乙氧基苯乙酮（DEAP）购自Alfa Asear。 丙烯酸（AAc），过硫酸钾（KPS），氯化钠（NaCl），N-（3-二甲基氨基丙基）-N'-乙基碳二亚胺盐酸盐（EDC）购自当地供应商。 通过从己烷/丙酮混合物中重结晶纯化NIPAM并在真空中干燥。 减压蒸馏AAc和HEMA。 其他试剂按原样使用。

Microgel Synthesis

Poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-AAc)) microgel was
synthesized by free radical precipitation polymerization. In brief, 1.400 g of NIPAM, 0.101 g of AAc, 0.032 g of BIS and 0.058 g of SDS were dissolved in 100 mL of water. The reaction mixture was transferred to a three-necked round-
bottom flask equipped with a condenser and a nitrogen line. The solution was purged with nitrogen and heated to 70°C. After 1 h, 0.081g KPS (dissolved in 2mL of water) was added to initiate the reaction. The reaction was allowed to proceed for 4 h. The resultant microgels were purified by dialysis against water with frequent water change for at least 2 weeks.
聚（N-异丙基丙烯酰胺 - 共 - 丙烯酸）（P（NIPAM-AAc））微凝胶是
通过自由基沉淀聚合合成。 简而言之，将1.400g NIPAM，0.101g AAc，0.032g BIS和0.058g SDS溶解在100mL水中。 将反应混合物转移至三颈圆形 -
底部烧瓶配有冷凝器和氮气管。 将溶液用氮气吹扫并加热至70℃。 1小时后，加入0.081g KPS（溶于2mL水中）以引发反应。 使反应进行4小时。 通过对水进行透析来对所得微凝胶进行纯化，频繁换水至少2周。

HEMA Modification

To 50 mL of purified P(NIPAM-AA) microgel dispersion 1.820 g of HEMA and 2.390 g of EDC were added. The reaction mixture was constantly stirred at room temperature for 4 hours. The resultant products were purified by dialysis against water with frequent water change for three days, lyophilized and stored in a refrigerator.
向50mL纯化的P（NIPAM-AA）微凝胶分散体中加入1.820g HEMA和2.390g EDC。 将反应混合物在室温下持续搅拌4小时。 通过对水进行透析来对所得产物进行纯化，频繁换水三天，冻干并储存在冰箱中。

Preparation of PMCC films

0.09 g of lyophilized HEMA-modified microgels were re-dispersed in 2 mL of deionized water, to which 0.24 μmol of DEAP (0.24 mol/L in DMSO) was added. The resulting solution was injected into 3 cm×1 cm×0.508 mm cuvettes. The samples were kept at room temperature and became iridescent in a few hours. They were then photopolymerized by exposure to UV light for 8 h (λ = 365 nm). The resulting films were released from the cuvettes and stored as freestanding films in water.
将0.09g冻干的HEMA-修饰的微凝胶再分散在2mL去离子水中，向其中加入0.24μmol的DEAP（在DMSO中0.24mol / L）。 将所得溶液注入3cm×1cm×0.508mm比色杯中。 将样品保持在室温下并在几小时内变成彩虹色。 然后通过暴露于UV光8小时（λ= 365nm）将它们光聚合。 将所得薄膜从比色皿中释放出来并作为独立薄膜储存在水中。

Characterizations

Fourier transform infrared (FTIR) spectra were measured on a Bio-Rad FTS-6000 spectrometer. 1H NMR spectra were recorded on a Varian UNITY-plus 400 NMR spectrometer using D2O as solvent. The hydrodynamic diameter (Dh) of the microgel particles were measured by dynamic light scattering with a Brookhaven 90Plus laser particle size analyzer. All the measurements were carried out at a scattering angle of 90°. The sample temperature was controlled with a build-in Peltier temperature controller. Reflection spectra of the PMCC films were measured with AvaSpec-2048 Fiber Optic spectrometer. The experimental setup was shown in Figure S4. The temperature of the sample cell was controlled with a refrigerated circulator.
在Bio-Rad FTS-6000光谱仪上测量傅里叶变换红外（FTIR）光谱。 使用D 2 O作为溶剂，在Varian UNITY-plus 400 NMR光谱仪上记录1 H NMR光谱。 用Brookhaven 90Plus激光粒度分析仪通过动态光散射测量微凝胶颗粒的流体动力学直径（Dh）。 所有测量均在90°的散射角下进行。 使用内置Peltier温度控制器控制样品温度。 用AvaSpec-2048光纤光谱仪测量PMCC膜的反射光谱。 实验装置如图S4所示。 用冷冻循环器控制样品池的温度。

Estimation of collective diffusion coefficient

集体扩散系数的估计

The collective diffusion coefficient D0 of the PMCC film was estimated according to Ref 30 in the text (Macromolecules 2009, 42, 9357). The characteristicn swelling time τ for a solid sphere with a radius R (a in Scheme S1) is determined by the following equation:

根据文中的参考文献30（Macromolecules 2009,42,9357）估计PMCC膜的集体扩散系数D0。 具有半径R的实心球的特征膨胀时间τ（方案S1中的a）由以下等式确定： For a spherical shell with an outer radius R and an inner radius r (b in Scheme S1), one may expect that2 ()shell Rr τ ∝−. In contrast, Ref 30 shows that 2 shell R τ ∝ , i.e, the characteristic swelling time of a gel shell is proportional to the square of the outer radius, not to the square of the shell thickness. They finally obtained the following equation for the characteristic swelling time of a gel shell: 对于具有外半径R和内半径r的球形壳（方案S1中的b），可以预期2（）壳Rrτα-。 相反，参考文献30显示2壳Rτα，即凝胶壳的特征溶胀时间与外半径的平方成比例，而不是壳厚度的平方。 他们最终获得了凝胶壳特征溶胀时间的下列等式：

Based on these findings, one can reasonably expect that the characteristic swelling time of a hemispherical gel shell (c in Scheme S1) is also proportional to the square of the outer radius, not to the square of the shell thickness. Since a planar hydrogel sheet (d in Scheme S1) can be regarded as a part of a spherical gel shell with a large curvature radius, one can further hypothesize that its characteristic swelling time is also proportional to the square of the side length, not to the square of the thickness. Therefore the collective diffusion coefficient D0 of the PMCC film can be estimated using Eq.(2).
基于这些发现，可以合理地预期半球形凝胶壳的特征溶胀时间（方案S1中的c）也与外半径的平方成比例，而不是与壳厚度的平方成比例。 由于平面水凝胶片（方案S1中的d）可以被认为是具有大曲率半径的球形凝胶壳的一部分，因此可以进一步假设其特征膨胀时间也与边长的平方成比例，而不是 厚度的平方。 因此，可以使用等式（2）估计PMCC膜的集体扩散系数D0。

Scheme S1. Hydrogels with various geometries. (a) solid sphere, (b) spherical shell, (c) hemispherical shell, and (d) planar sheet.
方案S1。 具有各种几何形状的水凝胶。 （a）实心球，（b）球形
壳，（c）半球壳，和（d）平板。

Figure S1. 1H NMR spectra of P(NIPAM-AAc) microgel and the HEMA-modified microgel. Solvent: D2O. Successful introduction of vinyl groups was confirmed by the appearance of new peaks at 6.11 and 5.66 ppm. The new peaks at 4.21 ppm(-O-CH2-CH2-O-) and 1.87 ppm(-CH3) further confirms the successful coupling of HEMA with the microgels. From the peak integration ratio of the peak at 4.21 ppm and the peak at 3.84ppm (CH(CH3)2 in NIPAM), it was estimated that ~23% of the AAc unit in the microgel reacted with HEMA.
图S1。 P（NIPAM-AAc）微凝胶和HEMA-修饰的微凝胶的1H NMR光谱。 溶剂：D2O。 通过在6.11和5.66ppm处出现新峰证实了乙烯基的成功引入。 在4.21ppm（-O-CH2-CH2-O-）和1.87ppm（-CH3）的新峰进一步证实了HEMA与微凝胶的成功偶联。 从峰值在4.21ppm和峰值在3.84ppm（在NIPAM中的CH（CH3）2）的峰积分比，估计微凝胶中约23％的AAc单元与HEMA反应。

Figure S2. FTIR spectra of P(NIPAM-AAc) microgel and the HEMA-modified microgel. The intensity of the peak at 1711 cm-1, which is assigned to the stretching of carboxylic acid groups, decreases significantly, suggesting the consuming of the carboxylic acid groups because of the coupling reaction.
图S2。 P（NIPAM-AAc）微凝胶和HEMA修饰的微凝胶的FTIR光谱。 1711cm -1处的峰强度（其归属于羧酸基团的拉伸）显着降低，表明由于偶联反应消耗了羧酸基团。

Figure S3. Bragg diffraction peak position of a PMCC film when temperature alternately changes from 19.0 to 23.8oC. The film is soaked in 0.5 M NaCl solution. pH=3.0.
图S3。 当温度交替从19.0℃变化到23.8℃时，PMCC膜的布拉格衍射峰位置。 将膜浸泡在0.5M NaCl溶液中。pH值= 3.0。

Figure S4. Experimental setup for the measurement of the reflection spectra of the PMCC films.
图S4。 用于测量PMCC膜的反射光谱的实验装置。