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Isothermal Crystallization Kinetics of α-Olefin Molecular Bottlebrushes
Macromolecules ( IF 5.1 ) Pub Date : 2020-08-20 , DOI: 10.1021/acs.macromol.0c01282 Carlos R. López-Barrón 1 , John R. Hagadorn 1 , Joseph A. Throckmorton 1
Macromolecules ( IF 5.1 ) Pub Date : 2020-08-20 , DOI: 10.1021/acs.macromol.0c01282 Carlos R. López-Barrón 1 , John R. Hagadorn 1 , Joseph A. Throckmorton 1
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The isothermal crystallization kinetics of a series of poly(α-olefin) bottlebrushes, with side-chain lengths (Nsc) ranging from 10 to 16 carbons, was systematically investigated via differential scanning calorimetry (DSC), small- and wide-angle X-ray scattering (SAXS/WAXS), small-angle light scattering (SALS), and polarized optical microscopy (POM). Analysis of the DSC data with the Avrami model reveals that crystallization proceeds via one-dimensional growth of rod-shaped crystallites (fibrils), which is unprecedented in semicrystalline polymers. Both the nucleation and crystallization rates, as well as the equilibrium melting temperature (obtained by the linear Hoffman–Weeks extrapolation method), are increasing functions of Nsc, which results from the decreasing energy barrier for crystallization as the side chains are longer. Analysis of the crystallization kinetics with the Lauritzen–Hoffman theory revealed two stages of crystallization. The transition from regime I to regime II occurs at undercooling values that decrease with Nsc and range from 10 K, for poly(1-octadecene), to 45 K, for poly(1-dodecene). Analysis of the crystal structure (via SAXS/WAXS, SALS, and POM) during isothermal crystallization showed an increase in crystallinity and a decrease in interfibril distance as undercooling deepens, as well as the development of bicontinuous crystal domains.
中文翻译：
α-烯烃分子刷的等温结晶动力学
通过差示扫描量热法（DSC），小角度和广角X系统研究了一系列侧链长度（N sc）为10至16个碳的聚（α-烯烃）牙刷的等温结晶动力学射线散射（SAXS / WAXS），小角度光散射（SALS）和偏振光学显微镜（POM）。使用Avrami模型对DSC数据进行分析后发现，结晶是通过一维生长的棒状微晶（原纤维）进行的，这在半结晶聚合物中是前所未有的。成核速率和结晶速率以及平衡熔化温度（通过线性霍夫曼–韦克斯外推法获得）都在增加N sc的功能。，这是由于侧链越长，结晶的能垒越低所致。用Lauritzen-Hoffman理论分析结晶动力学，揭示出结晶的两个阶段。从状态I到状态II的过渡发生在过冷值，该值随N sc减小，范围从10 K（对于聚（1-十八碳烯）到45 K，对于聚（1-十二碳烯）。等温结晶过程中的晶体结构分析（通过SAXS / WAXS，SALS和POM）显示，随着过冷程度的加深，结晶度增加，纤维间距离减小，并且出现了双连续晶体域。
更新日期：2020-09-09
中文翻译：
α-烯烃分子刷的等温结晶动力学
通过差示扫描量热法（DSC），小角度和广角X系统研究了一系列侧链长度（N sc）为10至16个碳的聚（α-烯烃）牙刷的等温结晶动力学射线散射（SAXS / WAXS），小角度光散射（SALS）和偏振光学显微镜（POM）。使用Avrami模型对DSC数据进行分析后发现，结晶是通过一维生长的棒状微晶（原纤维）进行的，这在半结晶聚合物中是前所未有的。成核速率和结晶速率以及平衡熔化温度（通过线性霍夫曼–韦克斯外推法获得）都在增加N sc的功能。，这是由于侧链越长，结晶的能垒越低所致。用Lauritzen-Hoffman理论分析结晶动力学，揭示出结晶的两个阶段。从状态I到状态II的过渡发生在过冷值，该值随N sc减小，范围从10 K（对于聚（1-十八碳烯）到45 K，对于聚（1-十二碳烯）。等温结晶过程中的晶体结构分析（通过SAXS / WAXS，SALS和POM）显示，随着过冷程度的加深，结晶度增加，纤维间距离减小，并且出现了双连续晶体域。
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