Analytical data belonging to the publication "Experimental determination of the bulk moduli of hollow nanogels as model system for nanocarriers"

The softness of an object can be quantified by one of the fundamental elastic moduli. The bulk modulus of the particle is most appropriate in the presence of isotropic compressions. Here, we use small-angle neutron scattering with contrast variation to directly access the bulk modulus of polymeric nanocapsules – pNIPAM-based hollow nanogels. We show that the size of the cavity is the most important quantity that determines the softness of hollow nanogels. During initial compression, the polymer collapses into the cavity and leads to a large change in the particle volume, resulting in a very small initial bulk modulus. Once the cavity is partially occupied by the polymer, the hollow nanogels become significantly stiffer since now the highly crosslinked network has to be compressed. Furthermore, we show that the larger the cavity, the softer the nanogel.

物体的柔软度可通过基础弹性模量之一进行量化。当发生各向同性压缩时，颗粒的体积模量（bulk modulus）最为适用。本研究采用带对比度变化的小角中子散射（small-angle neutron scattering），直接测得基于聚N-异丙基丙烯酰胺（pNIPAM）的空心纳米凝胶——即聚合物纳米胶囊——的体积模量。研究证实，空腔尺寸是决定空心纳米凝胶柔软度的核心影响因素。在初始压缩阶段，聚合物会向空腔内塌陷，导致颗粒体积发生显著变化，从而使初始体积模量极低。一旦空腔被聚合物部分填充，空心纳米凝胶的刚度会显著提升，因为此时需要对高度交联的聚合物网络进行压缩。此外，本研究还表明，空腔体积越大，纳米凝胶的柔软度越高。