Two-dimensional polymer

A two-dimensional polymer (2DP) is a sheet-like monomolecular macromolecule consisting of laterally connected repeat units with end groups along all edges.

[3][4][5][6] According to this, covalent long chain molecules ("Makromoleküle") do exist and are composed of a sequence of linearly connected repeat units and end groups at both termini.

Upon thermal activation of porphyrin building blocks, covalent bonds form to create a conductive polymer, a versatile route for bottom-up construction of electronic circuits has been demonstrated.

Covalent assembly to form 2D COFs has been previously done using boronate esters from catechol acetonides in the presence of a lewis acid (BF3*OEt2).

To design artificial assemblies capable of high selectivity requires correct manipulation of energetic and stereochemical features of non-covalent forces.

[14] An example of utilizing surface structures through non-covalent assembly uses adsorbed monolayers to create binding sites for target molecules through hydrogen bonding interactions.

Hydrogen bonding is used to guide the assembly of two different molecules into a 2D honeycomb porous network under ultra high vacuum seen in figure 8.

[14] 2D polymers based on DNA have been reported [15] 2DPs as two dimensional sheet macromolecules have a crystal lattice, that is they consist of monomer units that repeat in two dimensions.

[16][17][18] In 2014 a 2DP was reported synthesised from a trifunctional photoreactive anthracene derived monomer, preorganised in a lamellar crystal and photopolymerised in a [4+4]cycloaddition.

[19] Another reported 2DP also involved an anthracene-derived monomer [20] 2DPs are expected to be superb membrane materials because of their defined pore sizes.

[21] Additionally, metal-organic surfaces have been synthesized with cobalt dithionlene catalysts for efficient hydrogen production through reduction of water as an important strategy for fields of renewable energy.

[24][25][26] Since then a number of important attempts were reported in terms of cross-linking polymerization of monomers confined to layered templates or various interfaces.

Structural difference between a linear and a two-dimensional (2D) polymer. In the former, linearly connecting monomers result in a thread-like linear polymer, while in the latter laterally connecting monomers result in a sheet-like 2DP with regularly tessellated repeat units (here of square geometry). The repeat units are marked in red, whereby the number n describes the degree of polymerization. While a linear polymer has two end groups, a 2DP has an infinite number of end groups that are positioned all along the sheet edges (green arrows).
Figure 2. Surface-mediated 2D polymerization scheme of the tetrafunctional porphyrin monomer.
2D polymerization under thermodynamic control (top) versus kinetic control (bottom). Solid black lines represent covalent bond formation
Synthetic scheme of covalent organic framework using boronic acid and hexahydroxytriphenylene .
Boronate ester equilibria used to prepare various 2D COFs
Synthetic scheme for metal organic framework (MOF) using hexahydroxytriphenylene (HHTP) and Cu(II) metal.
Supramolecular aggregates of (CA*M) cyanuric acid (CA) and melamine (M).
Self-assembly of a PTCDI–melamine supramolecular network. Dotted lines represent the stabilizing hydrogen bonds between the molecules.