There is a concept known as [strange matter][1] which has been theorized based on our mathematical models of nuclear physics, though never observed. It would be a sort of "liquid" made of [quarks][2] which aren't confined to protons and neutrons, and it's been theorized that forms of it could be stable at low temperatures and pressures--for example, [this paper][3] says "Witten has pointed out that strange quark matter might be stable at a zero temperature and at a zero external pressure." $\text{*}$ (In fact, the analysis indicates it should be *more* stable than ordinary matter under these conditions since as mentioned [here][4] it would be the 'ground state' of matter made of quarks, meaning it would have lower potential energy than quarks confined to protons and neutrons. As discussed in [this answer][5] from the physics stack exchange, the idea is that ordinary matter is "metastable", having a potential barrier that tends to prevent it from decaying to strange matter unless it temporarily gains enough energy to hop the barrier, or unless you wait a sufficiently huge time for it to [get through the barrier via quantum tunneling][6]) 

[This PhD thesis][7] on strange matter in astrophysics has a section on p. 22-27 where it divides strange matter into some categories based on size, the largest being "bulk strange matter" with mass equivalent to over $10^{44}$ protons, which would again be "stable at zero temperature and pressure" along with very small strangelets with mass comparable to "isotopes of super-heavy elements" and an intermediate size with mass less than $10^7$ protons but larger than the very small category, which would have a radius of the order of a few hundred femtometers (a femtometer is a millionth of a nanometer). It's mentioned that for the intermediate size, "The electrons will now be found ‘orbiting’ the strangelet as in an atom", so maybe there could be a sort of "chemistry" with materials made up of multiple strangelets of this size bonded into "molecules" of a sort, although maybe the attraction would be too weak given their large mass or maybe they would just group together into bulk strange matter under these conditions, I couldn't find any info on this. Either way, bulk strange matter might have the features you're looking for. 

It's mentioned on p. 29 of [this paper][8] that negatively charged bulk strange matter would have disastrous consequences in the real world, since "ordinary atoms would be attracted to it and absorbed" (converted into strange matter themselves), but that for positively charged bulk strange matter, "a Coulomb barrier prevents this system from absorbing the nuclei or ordinary atoms" (and there are [theoretical and observational arguments][9] against negatively-charged strange matter being stable enough to 'infect' ordinary matter in this way). It's also mentioned that "since it is very dense even small chunks cannot be supported by material forces at the Earth's surface." This would suggest a problem with using such matter for construction on planets, and would also greatly add to a spacecraft's mass which would increase the fuel needed to accelerate it, but perhaps one could imagine using it to plate space stations as a form of armor (and I'm also not sure how think a later of strange matter could potentially be, perhaps thin enough that the mass wouldn't be so large even for a largish area being plated). Another interesting science-fictional use for very small bits of strange matter could be to create some form of ultra-tiny machines much smaller than nanotechnology, the notion of "femtotechnology" discussed in [this article][10], which could function at low pressure and temperature.

$\text{*}$*That quote only mentions stability at zero temperature, which is apparently simpler to analyze mathematically, but I found [this paper][11] which discusses stability at higher temperatures. I don't really understand what parameters are being graphed on the horizontal and vertical axes in the bottom left part of Fig. 1 on page 3, but it appears qualitatively as if "stability window"--the range of values of the parameters for which strange matter is stable--changes only slightly between T=0 and T=10 MeV, and according to the conversion [here][12] a temperature of 1 Kelvin corresponds to 0.0000862 eV, so 10 MeV = $10^7$ eV would be about 116 billion degrees Kelvin, suggesting you only have to worry about temperature affecting stability in extremely high-temperature cases. Page 120 of [this book][13] mentions that understanding how stability changes with temperature "is important since we shall in fact be looking at nuggets in hot environments such as the Big Bang and supernova-explosions."*


  [1]: http://en.wikipedia.org/wiki/Strange_matter
  [2]: http://en.wikipedia.org/wiki/Quark
  [3]: http://www.jetpletters.ac.ru/ps/1224/article_18487.pdf
  [4]: http://lss.fnal.gov/archive/1991/conf/Conf-91-349-A.pdf
  [5]: https://physics.stackexchange.com/a/238151/59406
  [6]: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/barr.html
  [7]: http://arxiv.org/abs/1408.6389
  [8]: http://chimera.roma1.infn.it/OMAR/dottorato/papers/jaffe_sqm_1.pdf
  [9]: https://physics.stackexchange.com/a/5101/59406
  [10]: http://hplusmagazine.com/2011/01/10/theres-plenty-more-room-bottom-beyond-nanotech-femtotech/
  [11]: http://arxiv.org/abs/1308.2079v1
  [12]: https://www.phys.ksu.edu/personal/cdlin/phystable/econvert.html
  [13]: http://books.google.com/books?id=YhNR_EbX5yoC&lpg=PP1&pg=PA120