Otto Schott Institute of Materials Research, Friedrich Schiller University, Fraunhoferstr. 6, 07743 Jena, Germany.
Institute of Organic Chemistry and Macromolecular Chemistry (IOMC), Friedrich-Schiller-University Jena, Lessingstraße 8, D 07443 Jena, Germany; Jena Center for Soft Matter (JCSM), Friedrich-Schiller-University Jena, Philosophenweg 7, D-07743 Jena, Germany.
Dent Mater. 2020 Mar;36(3):377-386. doi: 10.1016/j.dental.2020.01.001. Epub 2020 Jan 25.
This work focuses on the influence of poly(acrylic acid) (PAA) architecture (linear or branched) on setting behavior and compressive strength of glass ionomer cements (GICs).
Branched and linear poly(acrylic acid)s were synthesized according to the Strathclyde methodology or by free radical polymerization. They were characterized by H-NMR spectroscopy and size exclusion chromatography to determine their molecular weight and size distribution. GIC setting was characterized by oscillating rheometry and time-dependent FTIR spectroscopy. In addition, compressive strength was tested on cylindrical samples (6 × 4 mm; n = 8/cement composition) after storage in deionized water at 37 °C for one day.
We used two different routes to prepare PAA. One direct route in order to provide straightforward access to branched PAA and a two-step approach in order to get more control about the PAA molecular weight using tert-butyl acrylate (tBA) for polymerization with subsequent deprotection. Using the second approach we obtained several linear PAA of which a mixture was used in order to mimic the molecular weight and size distribution of branched PAA. This allowed the direct comparison of properties relying only on the polymer architecture. Comparing linear PAA to branched samples in general led to faster setting but at the same time decreased the compressive strength. Increasing molecular weight of branched PAA resulted in even faster GIC setting while increasing compressive strength and this correlates well with the trends reported for linear PAA in literature. Mixing of branched and linear PAA, however, turned out to be an effective way of tailoring GIC properties.
our results suggest that both molecular weight and dispersity need to be considered when choosing suitable PAA architecture for obtaining specific GIC properties.
本工作重点研究聚（丙烯酸）（PAA）结构（线性或支化）对玻璃离子水门汀（GIC）凝固行为和抗压强度的影响。
根据 Strathclyde 方法或自由基聚合合成支化和线性聚（丙烯酸）。通过 H-NMR 光谱和尺寸排阻色谱法对其分子量和分子量分布进行了表征。通过振荡流变仪和时间相关的傅里叶变换红外光谱法对 GIC 的凝固行为进行了表征。此外，在 37°C 的去离子水中储存一天后，在圆柱形样品（6×4mm；n=8/水泥组合物）上测试抗压强度。
我们使用了两种不同的方法来制备 PAA。一种是直接路线，以便直接制备支化 PAA；另一种是两步法，以便使用叔丁基丙烯酸酯（tBA）聚合并随后脱保护，从而更好地控制 PAA 的分子量。使用第二种方法，我们得到了几种线性 PAA，其中一种混合物用于模拟支化 PAA 的分子量和分子量分布。这使得仅依赖于聚合物结构的性质可以进行直接比较。通常，将线性 PAA 与支化样品进行比较会导致更快的凝固，但同时会降低抗压强度。增加支化 PAA 的分子量会导致 GIC 更快凝固，同时提高抗压强度，这与文献中报道的线性 PAA 的趋势非常吻合。然而，支化和线性 PAA 的混合被证明是一种调整 GIC 性能的有效方法。
我们的结果表明，在选择适合获得特定 GIC 性能的 PAA 结构时，分子量和分散度都需要考虑。
