Molecular origin of the foam structure in model linear and comb polystyrenes: I. Cell density
Molecular origin of the foam structure in model linear and comb polystyrenes: I. Cell density
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DOI：
10.1016/j.polymer.2020.122351
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发表时间：
2020-04
期刊：
影响因子：
4.6
通讯作者：
M. Abbasi;Lorenz Faust;M. Wilhelm
中科院分区：
文献类型：
--
作者：
M. Abbasi;Lorenz Faust;M. Wilhelm
以CO2为发泡剂，在间歇式发泡装置中研究了阴离子法合成的线型和梳形无规聚苯乙烯（PS），以及实验室规模的乳液聚合PS和商业PS的分子结构对泡沫泡孔密度（单位体积纯聚合物的泡孔数）的影响。在一系列具有相同缠结主链（Mw，bb ≤ 290 kg/mol，Zbb ≤ 20缠结）和类似支链（Mw，br ≤ 44 kg/mol，Zbr ≤ 3缠结，但支链数不同，3 ≤Nbr≤ 190）的梳形PS中，分子量Mw、分散度（Mw）、低分子量组分（即低聚物和残余表面活性剂）和每个分子的长链支链数NBR的影响。对细胞密度的影响。用三种不同的方法制备了用于发泡的样品，得到了未纯化、经处理和纯化的样品。良好纯化的样品产生泡孔密度高于109 cell/cm 3的泡沫，而未纯化的PS产生的泡沫的泡孔密度低一到三个数量级。然而，人工添加6重量%的低聚物PS或3重量%的表面活性剂的纯化的样品没有降低细胞密度显着。通过仅将PS溶解在溶剂中然后去除溶剂制备的处理样品产生的泡沫的泡孔密度略低于纯化的PS，约5 × 108个泡孔/cm 3。未纯化PS中较低的细胞密度被认为与连续离子薄膜层（例如表面活性剂）的形成有关，而不仅仅与聚合物中作为杂质的低分子量组分的存在有关。在不存在这种低分子量组分的情况下，其它分子参数，即Mw、Mw和Mw，这些系列的梳状PS令人惊讶地对泡孔密度没有明显的影响。
The effect of the molecular architecture of anionically synthesized linear and comb atactic polystyrenes (PS), as well as lab-scale emulsion polymerized PS and commercial PS on the cell density of foam (number of cells per unit volume of neat polymer) was investigated using CO2as foaming agent in a batch foaming setup. The effects of molecular weight,Mw, dispersity (Ð), low molecular weight components, i.e. oligomers and residual surfactant, and the number of long chain branches per molecule,Nbr, in a series of comb-PS with the same entangled backbone,Mw,bb≈ 290 kg/mol,Zbb≈ 20 entanglements, and similar branches,Mw,br≈ 44 kg/mol,Zbr≈ 3 entanglements, but different numbers of branches, 3 ≤Nbr≤ 190, on the cell density were investigated. Specimens for foaming have been prepared with three different methods, which resulted in non-purified, treated, and purified samples. Well-purified samples produced foams with cell density above 109cell/cm3, while foams out of the non-purified PS had one to three orders of magnitude lower cell density. However, artificial addition of 6 wt% oligomer PS or 3 wt% surfactant to the purified samples did not reduce the cell density significantly. Treated samples prepared by only dissolving the PS in a solvent followed by removing the solvent, produced a foam with slightly lower cell density, ~5 × 108cell/cm3, than the purified PS. Lower cell density in non-purified PS was supposed to be related to the formation of a continuous ionic thin film layer (e.g. surfactant) rather than only the presence of low molecular weight components as impurity in the polymer. In the absence of such low molecular weight components, other molecular parameters, i.e.Mw,Ð, andNbrin these series of comb-PS had surprisingly no distinct effect on the cell density.