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Dendrimer--Introduction to Hyperbranched Polymers

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| 2016-11-25 | Dendrimer--Introduction to Hyperbranched Polymers | 2016-11-25 |
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Hyperbranching, as a kind of dendrimer, is structurally an imperfect symmetrical dendrimer, but it has the same physical and chemical properties as a perfect dendrimer. ABx (X≥2) type monomer polycondensation reaction produces a soluble highly branched polymer. This polymer is not a perfect dendrimer, but a polymer with a defective structure. This polymer is called hyperbranched polymer.

In terms of titles, there are dozens of different names at home and abroad for hyperbranched polymers, mainly called by people, for example: hyperbranched polymers, hyperbranched macromolecules, hyperbranched compounds, hyperbranched molecules, hyperbranched

Physical and chemical properties

★ Highly branched structure

★ With a large number of functional groups in the molecule

★ There are three types of structural units in the molecule

★ Lower viscosity

★ Good solubility

history

Development of hyperbranched polymer

At the end of the 9th century, Berzelius reported resins synthesized from tartaric acid and glycerin.

In 1901, Wasten Smith reported the reaction of phthalic anhydride or phthalic acid with glycerol.

In 1952, Flory proposed that highly branched polymers could be prepared from polyfunctional monomers. But over the past few decades, highly branched polymers have not caught the attention.

It wasn't until the mid-1980s that DuPont's Wa Kim and others purposely synthesized a hyperbranched polymer and applied for the first patent in this regard, and the National Chemical Conference was held in Los Angeles in 1988. The results were announced on. In the early days, it was mainly the study of dendrimers.

Since then, research on hyperbranched polymers has sprung up. National governments and research institutes have successively established project teams to carry out in-depth research on technology synthesis, process exploration, and application value. Domestic and foreign companies (such as DSM in the Netherlands, Weihai Chenyuan New Materials, etc.) have also started projects to implement industrialized production and promote market applications.

Synthesis Progress

★ ABx monomers have pioneered the synthesis of hyperbranched polymers.

★ Ring-opening polymerization extends it to the field of cyclic compounds.

★ SCVP successfully applied vinyl monomers to the synthesis of hyperbranched polymers, and developed a new AB3 monomer method.

★ Development and application of A2 + B3 monomer synthesis method and effective control will industrialize hyperbranched polymers

The prospect has taken a big step forward.

★ The coupling monomer rule is a new method developed by combining the advantages of several previous synthetic methods. It uses a method similar to ring-opening polymerization to generate ABx monomers in situ, combining the respective A2 + B3 monomers and ABx monomers. The advantages, while overcoming their respective shortcomings to a certain extent, have pushed the research of hyperbranched polymers to a new level.

Application area

Coating industry

Low viscosity makes hyperbranched polymers very suitable for applications in high solids coatings. It can be blended with linear polymer coatings to reduce system viscosity and improve system fluidity; high solubility can reduce the amount of solvent and reduce costs. Reduce harmful gas emission; highly branched structure makes less chain entanglement between hyperbranched polymer molecules, not easy to crystallize, so that the coating has good film-forming performance; numerous end-group functional groups make hyperbranched polymer coating It can be modified to prepare coatings suitable for various applications. Because of these, hyperbranched polymers can be applied to a variety of coating resin systems.

2. Processing Aid

Hyperbranched polymers have a lower melt viscosity and have great potential for improving the processing properties of traditional polymers. Thermosetting resins are widely used in the development of composite materials due to their excellent thermodynamic properties and good injection characteristics. However, their relatively low toughness and damage resistance often limit their applications. Its toughness properties can be changed by adding hyperbranched polymers, and after adding additives, the toughening system does not affect the excellent thermodynamic properties of thermoset materials. Compared with styrene homopolymers, the blends obtained by blending hyperbranched polybenzene with linear styrene have reduced viscosity at high temperatures, increased shear rate and stability without affecting mechanical properties.

3. Enzyme carrier

The surface of hyperbranched macromolecules is determined by the topological arrangement of the end groups, so degradable hyperbranched macromolecules can be used as a template to create nano-sized cavities. If the degraded back-end group is still connected to the matrix, a precisely controlled cavity with special chemical groups on the wall can be obtained. This makes sense for mimicking enzyme, catalyst, and molecular separations.

4. Photoelectric materials

Due to the good solubility and processability of hyperbranched polymers, three-dimensional hyperbranched conjugated polymers have attracted attention as a new optical, electrical, and magnetic material. Due to their unique structure, they can show better performance than conventional linear light-emitting polymers. They may have excellent color adjustability, effective charge transportability, and good processability.

5. Hyperbranched liquid crystal polymer

The phase transition temperature of the hyperbranched macromolecular liquid crystal is generally limited, and even overlaps with the glass transition temperature, which affects the application range of the hyperbranched macromolecular liquid crystal. The flexibility of the molecules synthesized by the new method, the branches of which will change the conformation and arrange them parallel to each other to reduce the free volume. This hyperbranched macromolecular liquid crystal exhibits nematic liquid crystal behavior in a wide temperature range (50-132 ° C).

6. Drug extended release

Hyperbranched polymers can be used as pharmaceutical carriers in the agricultural, cosmetic and pharmaceutical industries. The "core" molecules of some hyperbranched polymers are highly hydrophobic and can be better compatible with hydrophobic drugs. The polyethylene glycol long chain outside the molecule is more hydrophilic and increases the hydrophobic drugs in polar media. Of solubility. By controlling the size and degree of branching of hyperbranched molecules, the distribution of slow-release drugs in the body can be controlled. Hyperbranched macromolecules that can be physically cross-linked with slow-release drugs can be designed to produce biocompatible small-molecule drugs after hydrolysis.

7. Molecular self-assembly

Self-assembly is a phenomenon in which the constituent elements of a system gather and organize themselves into a regular structure without the intervention of external forces. The occurrence of self-assembly procedures usually transforms the system from an disordered (ordered) state to an ordered (ordered) state. It can occur at different scales. For example, the molecules first aggregate into nano-sized supermolecular units. The forces between these supermolecular units further promote their regular arrangement in space, giving the system a hierarchical structure. structure).

Outlook

Hyperbranched polymers have properties that other forms of polymers do not have because of their unique structural morphology, and their special applications in various fields are also gradually expanding. No matter in theoretical research or application, hyperbranched polymers show great prospects. Its versatility and potential application possibilities make it a very active research field and will bring other fields Significant impact.

In the future, the development of hyperbranched polymers will mainly focus on the following aspects:

(1) Enrich the types of hyperbranched polymers;

(2) Development of new synthetic methods;

(3) establish a new theoretical system and characterization methods;

(4) Expand and deepen application fields.

Chen Yuan molecular profile

1. Asian enterprises that realize the industrial production of dendrimers, academician workstations in the field of dendrimers;

2. The product leads the reform of the new materials industry. Compared with traditional materials, the performance is improved by more than 30% and the core competitiveness is improved;

3. The product technology is the precipitation and accumulation of more than 20 years of research and development experience of Chenyuan Company and Peking University, and the product performance is stable;

4. Fortune 500 partners, such as Huntsman, Sinopec, PetroChina, GE, etc .;

5. A management team composed of executives from Dow Chemical, Rohm and Haas, Arkema, France, and Atofina.

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