Polymer Industry

Glycocalyx, the carbohydrate coat on cell surface, has been proved particularly important in a variety of biological events. In this work, polymeric vesicle mimicking glycocalyx (PV-Gx), as a simplified model system, is achieved via our NCCM strategy, using dynamic covalent bond between phenylboronic acid and sugar as the non-covalent linkage. Dynamic light scattering (DLS) has been employed to monitor the binding process between the sugars on PV-Gx and three different lectins. The results clearly proved that the PV-Gx constructed from the polymers with well-defined sugar units is a promising platform for the study of carbohydrate-protein interactions in solution without fluorescent labeling of proteins.

Su L, Zhao Y, Chen GS, Jiang M. Polym. Chem., 2012, DOI:10.1039/C2PY20110K.

Aspects of the self-assembly of particles, which uses nanometer or micrometer sized building blocks to bridge the gap between microscopic and macroscopic scales, are reviewed. Particle self-assembly has been the focus of considerable research in recent years because it can lead to superstructures with a complexity inaccessible by molecular self-assembly, and functionalities entirely different from or superior to those of the primary particles. Examples in molecular self-assembly suggests that anisotropic interactions could be useful in promoting particle self-assembly, with the exception of colloidal crystallization, which requires particles of uniform size and shape. Anisotropic particles prepared by surface modification of precursor particles are often rigid and submicron or micron sized, and thus relatively strong isotropic van der Waals interactions tend to resist self-assembly into regular superstructures. In addition, the relatively large contact area between particles needed for a sufficient binding enthalpy to stabilize a superstructure is difficult for rigid spherical particles. In contrast, flexible anisotropic polymeric particles dispersed in solvents have been shown to self-assemble into various superstructures. The flexibility of primary anisotropic particles enables them to fuse and stabilize into a superstructure. Some flexible and multicomponent particles that are isotropic in common solvents can undergo deformation and sufficient material redistribution to anisotropically self-assemble into regular superstructures in selective solvents. The self-assembly is also driven by anisotropic interactions, which is induced during self-assembly rather than in the particles as synthesized. This review focuses on recent achievements in soft particle self-assembly and describes briefly the advancements in rigid particle self-assembly. The presentation is divided into discussion of self-assembly by the colloidal crystallization of isotropic rigid particles, anisotropic rigid particles, anisotropic soft particles and isotropic soft particles, in that order.

Zhang KK, Jiang M, Chen DY. Prog. Polym. Sci. 2011, DOI:10.1016/j.progpolymsci.2011.09.003

Asymmetrically modified PNIPAM (Mw 10K), i.e. C₁₂-PNIPAM-CA with a hydrophobic hydrocarbon chain -C₁₂H₂₅ (C12) at one end and a hydrophilic carboxyl group -COOH (CA) as the other, was prepared and found to form micelles with a core of the lightly associated hydrocarbon chains. When temperature is increased to the LCST of PNIPAM, the transformation from micelles to vesicles can be realized within 30 min, while the reverse process only takes a few minutes. Based on full monitoring of the transition process, it is proposed that the micelles serve as building blocks in constructing the vesicles via processes of combination, fusion, and etc., in which only local conformation adjustment of PNIPAM is involved.

Wei KC, Su L, Chen GS and Jiang M. Polymer, 2011, 52, 3647-3654.

In this invited review, we address how inclusion complexation has been employed and used to promote the recent developments in macromolecular self-assembly, especially with responsive functionalities. These include the amphiphilicity adjustment of macromolecules, non-covalent linkages for forming pseudo block copolymers and micelles, surface modification and functionalization of polymeric micelles and vesicles, and the combination of synthetic polymeric assemblies with biological moieties.

Chen GS, Jiang M*, Chem. Soc. Rev. 2011, 40, 2254-2266.

A photo reversible hydrogel has been achieved via supramolecular competition. Briefly, a pseudopolyrotaxane Hydrogel formed by the inclusion complexation between α-cyclodextrin and poly(ethylene glycol) (PEG). After trans-azobenzene (trans-Azo) was added, the hydrogel transformed to solution because of the stronger binding ability of trans-Azo with α-CD than PEG. After UV light irradiation, trans-Azo isomerized to its cis form, which can not hold a-CD any more, which induced the formation of hydrogel again.

Liao XJ, Chen GS, Liu XX, Jiang M. Angew. Chem. Int. Ed. 2010, 49, 4409 –4413.

A novel dual-responsive supramolecular hydrogel composed of an azobenzene (AZO) end- functionalized block copolymer PDMA-b-PNIPAM (AZO-(PDMA-b-PNIPAM)) and β-cyclodextrin-modified CdS quantum dot (β-CD@QD) has been demonstrated. Based on the host-guest inclusion complexation of AZO of the block copolymers and CD cavities on β-CD@QD, they form a hybrid inclusion complex (HIC). The inclusion complex and the domains of the collapsed PNIPAM chains serve as two distinct crosslinks and render the hydrogel excellent dual sensitivity to competitive hosts/guests substitution and to temperature variation.

Liu JH, Chen GS, Guo MY,  Jiang M. Macromolecules. 2010, 43, 8086-8093.

Nearly ten years ago, we suggested a new concept of non-covalently connected micelles (NCCMs) to describe and name a novel family of polymeric micelles. In NCCMs the components that form the core and shell are connected by hydrogen bonding instead of the normal covalent bonding that exists in all micelles formed from block copolymers. Investigations by us, as well as by others, in recent years have shown that the concept of NCCMs, and the methodology to attain them, are in fact much broader than our original suggestion.

Guo MY and Jiang M.Soft Matter 2009, 5, 495-500

Functional nanohybrids self-assembly from amphiphilic calix[6]biscrowns and noble metals
Bing Guan, Qing Liang, Yuan Zhu, Minghua Qiao, Jiong Zou and Ming Jiang

One-dimensional nanohybrids made of organic templates of calixcrowns and in-situ formed metal nanoparticles were fabricated. The structure and catalytic properties of the hybrids were investigated.

Guan B, Liang Q, Jiang M, et al.JOURNAL OF MATERIALS CHEMISTRY 2009,19, 7610-7613

β-Cyclodextrin (β-CD)-ended linear poly(N-isopropylacrylamide) (β-CD-PNIPAM) and Frechet-type benzyl ether dendron with an azobenzene group (Gx-Azo) at the apex site form noncovalently connected amphiphiles (NCCAs) by inclusion complexation between the azo group and β-CD. The NCCAs self-assemble into vesicles in water. Optical switching of the assembly and disassembly is realized by alternating visible andUVirradiation, which causes the isomerization of the azo groups and their consequent complexation and decomplexation with β-CD. The structure and morphology of the vesicles were characterized by dynamic light scattering (DLS), static light scattering (SLS), SEM, TEM, and AFM. These photoresponsive vesicles can further respond to heat stimuli resulting in reversible aggregation and disaggregation of the vesicles.

Zou J, Guan B, Jiang M, et al. Macromolecules 2009, 42, 7465-7473

In conclusion, to our knowledge, this communication presents the first example of a morphological transition from vesicles to nanotubes in self-assemblies of calixarenes. Unlike the remarkably broad and deep studies on self-assembly of block copolymers which started in the 1970’s, the investigation on self-assembly of the calixarenes is still at the very beginning. Great efforts are needed to exploit the relationship between the resultant morphologies and the structural parameters of the calixarenes, including the conformation of the framework, the structure and length of the attached hydrophilic chains etc, some of which is currently underway in our laboratory.

As schematically summarized in Scheme 2, a novel kind of vesicle, which is reactive in supramolecular chemistry, was prepared through β-CD-ended polyether imide in water. On both the outer and inner surfaces of the vesicles, β-CD cavities are available for further surface modification via inclusion complexation between β-CD and adamantane-monoended PEG. For Ada-PEG2K and Ada-PEG1.1K, both the inner andouter surfaces can be fully modified whereas for Ada-PEG5K the inner surfaces can be only partially modified. We emphasis that our surface modification of the vesicles is completely based on supramolecular chemistry and thus the guest polymers are no covalently connected to the surfaces. This study opens a new, simple, mild avenue to the surface modification and functionalization of the vesicles, which of course would promote their applications in various areas.

Mingyu, Guo; Ming, Jiang; Guangzhao, Zhang,LANGMUIR   24(7)  10583

In summary, reversible thermochromism was achieved in hierarchically self-assembled PVP/PDA nanoaggregates using a hydrogen-bonding-assisted NCCM approach. Intriguingly, a “bricks and mortar” structure in PVP/DA nanoaggregates was obtained by annealing the sample at a temperature (65°C)
slightly higher than the melting point of pure DA crystals (63°C). After topochemical polymerization, the resultant PVP/PDA “bricks and mortar” structurewas further stabilized at high temperatures (up to 120°C). Contrary to pure irreversible PDA crystals, PVP-intercalated PDA nanoaggregates showed reversible
thermochromic transitions in both aqueous suspension and dry films. The cooperative interaction between PVP and PDA through tethering carboxylic acid head groups in the side chains of PDA to PVP layers via hydrogen bonding is believed to be responsible for reversible conformational transitions between the “red” and “blue” states. This study not only opens a new avenue for further understanding of reversible thermochromism in polydiacetylenes but also leads to more effective ways of preparing thermally reversible polydiacetylene-based materials utilizing commercially available polymers and diacetylene monomers.