Determination of the Molecular Weight of Conjugated Polymers with Diffusion-Ordered NMR Spectroscopy
Determination of the Molecular Weight of Conjugated Polymers with Diffusion-Ordered NMR Spectroscopy
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DOI：
10.1021/acs.chemmater.7b05063
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发表时间：
2018-02-13
影响因子：
8.6
通讯作者：
Loo, Yueh-Lin
中科院分区：
文献类型：
--
作者：
Gu, Kaichen;Onorato, Jonathan;Loo, Yueh-Lin
尺寸排除色谱（SEC）不适合表征共轭聚合物的分子量（MW）和分子量分布，特别是那些在检测波长处强吸收的聚合物，或那些与SEC柱壁相互作用和吸附的聚合物。我们证明了扩散有序核磁共振波谱（DOSY）作为表征共轭聚合物尺寸和尺寸分布的补充方法。以四批具有明显窄谱分布的聚（3-己基噻吩）为模型体系，通过DOSY方法建立了重量平均谱与扩散系数之间的幂律关系。我们将这种方法扩展到表征聚[4-（4,4-二十六基- 4h -环戊[1,2-b:5,4-b']二噻吩-2-基）-alt-[1,2,5]噻二唑-[3,4-c]吡啶]，其吸收特性使其无法用基于光散射的技术进行表征，包括SEC。通过对DOSY测量获得的扩散系数应用相同的幂律，我们提取了六个不同批次PCDTPT的p3ht等效MW和MW分布。通过规避SEC测量中的实际问题，DOSY有望成为确定聚合物尺寸的通用补充。
Size exclusion chromatography (SEC) is not well suited for characterizing the molecular weight (MW) and MW distribution of conjugated polymers, especially those that absorb strongly at the detection wavelengths, or those that interact with and adsorb on the walls of SEC columns. We demonstrate diffusion-ordered NMR spectroscopy (DOSY) as a complementary method for characterizing the size and size distribution of conjugated polymers. Starting with four batches of poly(3-hexylthiophene), whose distinct and narrow MW distributions had been fully characterized, as a model system, we establish a power-law relationship between the weight-average MW and the diffusion coefficient measured through DOSY. We extend this approach to characterizing poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiadiazolo-[3,4-c]pyridine], whose absorption properties preclude its characterization with light scattering based techniques, including SEC. By applying the same power law on the diffusion coefficients obtained by DOSY measurements, we extracted P3HT-equivalent MWs and MW distributions for six different batches of PCDTPT. By circumventing the practical issues in SEC measurements, DOSY shows promise as a versatile complement for determining polymer size.