Features determining aggregate structure

The subject of hydrogen bond (or bonding) is certainly a popular one. The ISI Science Citation database lists more than 26,000 papers that use this phrase in the title, abstract, or as a keyword. In the year 1999 alone there were about 3,000 such papers published. The importance of the hydrogen bond stems mainly from the fact that for certain types of molecules formation of such bonds determines the structure of the dimers or of larger molecular clusters. Thus, hydrogen bonds are characteristic features of many clusters, biological aggregates, and of condensed phases. 

Crystals of high purity metals are very soft, while high purity diamond crystals are very hard. Why are they different What features of the atomic (molecular) structures of materials determine how hard any particular crystal, or aggregate of crystals, is Not only are crystals of the chemical elements to be considered, but also compounds and alloys. Glasses can also be quite hard. Is it for similar reasons What about polymeric materials ... 

Thus, when PS solutions are used as a dispersion medium, the size of die carbon structures formed depends on polymer concentration the lower it is, the more features corresponding to aggregates of Si02 particles. The fine structure of carbon features depends on the structure of PS adsorption layers and is determined by the supramolecular structure of the polymer solutions used. 

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