Pipertzis Achilleas, Chroni Angeliki, Pispas Stergios, Swenson Jan
Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Ave., 11635 Athens, Greece.
J Phys Chem B. 2024 Nov 14;128(45):11267-11276. doi: 10.1021/acs.jpcb.4c05398. Epub 2024 Nov 5.
We investigate the self-assembly and dynamics of double hydrophilic block copolymers (DHBCs) composed of densely grafted poly[oligo(ethylene glycol) methacrylate] (POEGMA) and poly(vinyl benzyl trimethylammonium chloride) (PVBTMAC) parent blocks by means of calorimetry, small- and wide-angle X-ray scattering (SAXS/WAXS), and dielectric spectroscopy. A weak segregation strength is evident from X-ray measurements, implying a disordered state and reflecting the inherent miscibility between the host homopolymers. The presence of intermixed POEGMA/PVBTMAC nanodomains results in homogeneous molecular dynamics, as evidenced through isothermal dielectric and temperature-modulated DSC measurements. The intermixed process undergoes a glass transition at a temperature approximately 40 K higher than the vitrification of bulk POEGMA segments, and it shifts to an even higher temperature by increasing the content of the hard block. At temperatures below the intermixed glass transition temperature, the confined POEGMA segments between the glassy intermixed regions contribute to a segmental process featuring (i) reduced glass transition temperature (), (ii) reduced dielectric strength, (iii) broader distribution of relaxation times, and (iv) reduced fragility compared to the POEGMA homopolymer. We also observe two glass transition temperatures of dry PVBTMAC, which we attribute to the backbone and side chain segmental relaxation. To the best of our knowledge, this is the first time in the literature that these glass transitions of dry PVBTMAC have been reported. Finally, this study shows that excellent mixing of the two homopolymers is obtained, and this implies that different properties of this copolymer system can be tailored by adjusting the concentration of each homopolymer.
我们通过量热法、小角和广角X射线散射（SAXS/WAXS）以及介电谱，研究了由密集接枝的聚[甲基丙烯酸寡聚（乙二醇）酯]（POEGMA）和聚（乙烯基苄基三甲基氯化铵）（PVBTMAC）母体嵌段组成的双亲水嵌段共聚物（DHBCs）的自组装和动力学。X射线测量结果表明存在较弱的相分离强度，这意味着体系处于无序状态，反映了主体均聚物之间固有的混溶性。POEGMA/PVBTMAC纳米域的相互混合导致了均匀的分子动力学，等温介电和温度调制DSC测量结果证明了这一点。相互混合过程在比本体POEGMA链段玻璃化转变温度高约40 K的温度下经历玻璃化转变，并且通过增加硬嵌段的含量，玻璃化转变温度会进一步升高。在低于相互混合玻璃化转变温度的温度下，玻璃态相互混合区域之间受限的POEGMA链段导致了一个链段过程，其特征在于：（i）玻璃化转变温度降低，（ii）介电强度降低，（iii）弛豫时间分布变宽，以及（iv）与POEGMA均聚物相比脆性降低。我们还观察到干燥PVBTMAC有两个玻璃化转变温度，我们将其归因于主链和侧链的链段弛豫。据我们所知，这是文献中首次报道干燥PVBTMAC的这些玻璃化转变。最后，这项研究表明两种均聚物实现了优异的混合，这意味着可以通过调整每种均聚物的浓度来定制该共聚物体系的不同性能。
