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Dendrimers
A dendrimer is generally described as a macromolecule, which is characterized by its highly
branched 3D structure that provides a high degree of surface functionality and versatility.
Dendrimers have often been refered to as the “Polymers of the 21st century”. Dendrimer
chemistry was first introduced in 1978 by Fritz Vogtle and coworkers. He synthesized the first
“cascade molecules”. In 1985, Donald A. Tomalia, synthesized the first family of dendrimers.
The word “dendrimer” originated from two words, the Greek word dendron, meaning tree, and
meros, meaning part. At the same time, Newkome’s group independently reported synthesis of
similar macromolecules. They called them arborols from the Latin word ‘arbor’ also meaning a
tree. The term cascade molecule is also used, but ‘dendrimer’ is the best established one. Due to
their multivalent and monodisperse character, dendrimers have stimulated wide interest in the
field of chemistry and biology, especially in applications like drug delivery, gene therapy and
chemotherapy.
Crystal structure of a first-generation polyphenylene dendrimer reported by Müllen et al.
Properties
Dendritic molecules are characterized by structural perfection. Dendrimers and dendrons are
monodisperse and usually highly symmetric, spherical compounds. The field of dendritic
molecules can be roughly divided into low-molecular weight and high-molecular weight species.
The first category includes dendrimers and dendrons, and the latter includes dendronized
polymers, hyperbranched polymers, and the polymer brush.
The properties of dendrimers are dominated by the functional groups on the molecular surface,
however, there are examples of dendrimers with internal functionality. Dendritic encapsulation
of functional molecules allows for the isolation of the active site, a structure that mimics that of
active sites in biomaterials. Also, it is possible to make dendrimers water soluble, unlike most
polymers, by functionalizing their outer shell with charged species or other hydrophilic groups.
Other controllable properties of dendrimers include toxicity, crystallinity, tecto-dendrimer
formation, and chirality.
Dendrimers are also classified by generation, which refers to the number of repeated branching
cycles that are performed during its synthesis.
Types of Dendrimers
1.
Pamam Dendrimer
Poly (amidoamine) dendrimers (PAMAM) are synthesized by the divergent method starting from
ammonia or ethylenediamine initiator core reagents. Products up to generation 10(7) (a molecular
weight of over 9,30,000 g/mol) have been obtained (by comparison, the molecular weight of
human hemoglobin is approximately 65,000 g/mol). PAMAM dendrimers are commercially
available, usually as methanol solutions. Starburst dendrimers is applied as a trademark name for
a sub-class of PAMAM dendrimers based on a tris-aminoethylene-imine core. The name refers
to the starlike pattern observed when looking at the structure of the high-generation dendrimers
of this type in two-dimensions.
2.
Pamamos Dendrimer
Radially layered poly(amidoamine-organosilicon) dendrimers (PAMAMOS) are inverted
unimolecular micelles that consist of hydrophilic, nucleophilic polyamidoamine (PAMAM)
interiors and hydrophobic organosilicon (OS) exteriors. These dendrimers are exceptionally
useful precursors for the preparation of honeycomb-like networks with nanoscopic PAMAM and
OS domains.
3.
PPI Dendrimer
PPI-dendrimers stand for “Poly (Propylene Imine)” describing the propylamine spacer moieties
in the oldest known dendrimer type developed initially by Vögtle. These dendrimers are
generally poly-alkyl amines having primary amines as end groups, the dendrimer interior
consists of numerous of tertiary tris-propylene amines. PPI dendrimers are commercially
available up to G5, and has found widespread applications in material science as well as in
biology. As an alternative name to PPI, POPAM is sometimes used to describe this class of
dendrimers. POPAM stands for Poly (Propylene Amine), which closely resembles the PPI
abbreviation. In addition, these dendrimers are also sometimes denoted “DAB-dendrimers”
where DAB refers to the core structure, which is usually based on Diamino butane.
4.
Tecto Dendrimer
These are composed of a core dendrimer, surrounded by dendrimers of several steps (each type
design) to perform a function necessary for a smart therapeutic nanodevice. Different compounds
perform varied functions ranging from diseased cell recognition, diagnosis of disease state drug
delivery, reporting location to reporting outcomes of therapy.
5.
Multilingual Dendrimers
In these dendrimers, the surface contains multiple copies of a particular functional group.
6.
Chiral Dendrimers
The chirality in these dendrimers are based upon the construction of a constitutionally different
but chemically similar branches to chiral core.
7.
Hybrid Dendrimers Linear Polymers
These are hybrids (block or graft polymers) of dendritic and linear polymers.
8.
Amphiphilic Dendrimers
They are built with two segregated sites of chain end, one half is electron donating and the other
half is electron withdrawing.
9.
Micellar Dendrimers
These are unimolecular micelles of water soluble hyper branched polyphenylenes.
10. Multiple Antigen Peptide Dendrimers
It is a dendron-like molecular construct based upon a polylysine skeleton. Lysine with its alkyl
amino side-chain serves as a good monomer for the introduction of numerous of branching
points. This type of dendrimer was introduced by J. P. Tam in 1988, has predominantly found its
use in biological applications, e.g. vaccine and diagnostic research.
Synthesis
The synthesis used for dendrimer preparation permit almost entire control over the critical
molecular design parameters such as size, shape, surface/interior chemistry, flexibility, and
topology. Many dendrimer syntheses rely upon traditional reactions, such as the Michael reaction
or the Williamson ether synthesis whilst others involve the use of modern techniques and
chemistry, such as solid-phase synthesis, organo-transition-metal chemistry, organosilicon
chemistry, organo-phosphorus chemistry, or other contemporary organic methodologies. The
choice of the growth reaction dictates the way in which the branching should be introduced into
the dendrimer. Branching may either be present in the building blocks as is more often the case
or it can be created as a function of the growth reaction, as is the case with the poly
(amidoamine)s and the poly (propylene imine)s.
1. ‘Divergent’ Dendrimer Growth
The synthetic methodology employed in the early dendrimer syntheses came to be known as the
'divergent' approach. This name comes from the way in which the dendrimer grows outwards
from the core, diverging into space. Starting from a reactive core, a generation is grown, and then
the new periphery of the molecule is activated for reaction with more monomers. The two steps
can be repeated. The divergent approach is successful for the production of large quantities of
dendrimers since, in each generation-adding step, the molar mass of the dendrimer is doubled.
Divergently grown dendrimers are virtually impossible to isolate pure from their side products.
The synthetic chemist must rely on extremely efficient reactions in order to ensure low
polydispersities. The first synthesized dendrimers were polyamidoamines (PAMAMs).They are
also known as starbust dendrimers. Ammonia is used as the core molecule & In the presence of
methanol, it reacts with methylacrylate and then ethylenediamine is added.
NH3 + 3CH2CHCOOCH3 N(CH2 CH2COOCH3)3
3 NH2 CH2 CH2NH2 N(CH2 CH2CONHCH2 CH2NH2)3 + 3CH3OH
At the end of each branch there is a free amino group that can react with 2 methyl acrylate
monomers and 2 ethylenediamine molecules. Each complete reaction sequence results in a new
dendrimer generation. The number of reactive surface sites is doubled with every generation
since the mass increases more than twice.
Divergent Dendrimer Growth
2. ‘Convergent’ Dendrimer Growth
The 'convergent' approach was developed as a response to the weaknesses of divergent
syntheses. Convergent growth begins at what will end up being the surface of the dendrimer, and
works inwards by gradually linking surface units together with more. When the growing wedges
are large enough, several are attached to a suitable core to give a complete dendrimer. The
advantages of convergent growth over divergent growth stem that only two simultaneous
reactions are required for any generation-adding step. The convergent methodology also suffers
from low yields in the synthesis of large structures. The convergent growth method has several
advantages:
1. Relatively easy to purify the desired product and the occurrence of defects in the final
structure is minimised.
2. Possible to introduce subtle engineering into the dendritic structure by precise placement of
functional groups at the periphery of the macromolecules.
3. Approach does not allow the formation of high generation dendrimer because stearic problems
occur in the reactions of the dendrons and the core molecule.
Convergent Dendrimer Growth
Two principle synthetic methods for constructing dendritic macromolecules (dendrons): (a)
the divergent method, in which the synthesis begins from a polyfunctional core and
continues radially outwards by successive stepwise activation and condensation, (b) the
convergent method in which the synthesis begins at what will be the periphery of the final
macromolecule and proceeds inwards.
Synthesis of commercially available PAMAM dendrimer.
3. ‘Double Exponential’ And ‘Mixed’ Growth
The most recent fundamental breakthrough in the practice of dendrimer synthesis has come with
the concept and implications of 'double exponential' growth. Double exponential growth, similar
to a rapid growth technique for linear polymers, involves an AB2 monomer with orthogonal
protecting groups for the A and B functionalities. This approach allows the preparation of
monomers for both convergent and divergent growth from a single starting material. These two
products are reacted together to give an orthogonally protected trimer, which may be used to
repeat the growth process again. The strength of double exponential growth is more subtle than
the ability to build large dendrimers in relatively few steps. In fact, double exponential growth is
so fast that it can be repeated only two or perhaps three times before further growth becomes
impossible. The double exponential methodology provides a means whereby a dendritic
fragment can be extended in either the convergent or the divergent direction as required. In this
way, the positive aspects of both approaches can be accessed without the necessity to bow to
their shortcomings.
Double Exponential and Mixed Growth
Applications
Applications of dendrimers typically involves conjugating other chemical species to the
dendrimer surface that can function as detecting agents (such as a dye molecule), affinity ligands,
targeting components, radioligands, imaging agents, or pharmaceutically active compounds.
Dendrimers have very strong potential for these applications because their structure can lead to
multivalent systems. In other words, one dendrimer molecule has hundreds of possible sites to
couple to an active species. Researchers aimed to utilize the hydrophobic environments of the
dendritic media to conduct photochemical reactions that generate the products that are
synthetically challenged. Carboxylic acid and phenol terminated water soluble dendrimers were
synthesized to establish their utility in drug delivery as well as conducting chemical reactions in
their interiors. This might allow researchers to attach both targeting molecules and drug
molecules to the same dendrimer, which could reduce negative side effects of medications on
healthy cells.
Dendrimers can also be used as a solubilizing agent. Since their introduction in the mid-1980s,
this novel class of dendrimer architecture has been a prime candidate for hosts’ guest chemistry.
Dendrimers with hydrophobic core and hydrophilic periphery have shown to exhibit micelle-like
behavior and have container properties in solution. The use of dendrimers as unimolecular
micelles was proposed by Newkome in 1985. This analogy highlighted the utility of dendrimers
as solubilizing agents. The majority of drugs available in pharmaceutical industry are
hydrophobic in nature and this property in particular creates major formulation problems. This
drawback of drugs can be ameliorated by dendrimeric scaffolding, which can be used to
encapsulate as well as to solubilize the drugs because of the capability of such scaffolds to
participate in extensive hydrogen bonding with water.
Gene delivery
The ability to deliver pieces of DNA to the required parts of a cell includes many challenges.
Current research is being performed to find ways to use dendrimers to traffic genes into cells
without damaging or deactivating the DNA. To maintain the activity of DNA during
dehydration, the dendrimer/DNA complexes were encapsulated in a water soluble polymer, and
then deposited on or sandwiched in functional polymer films with a fast degradation rate to
mediate gene transfection. Based on this method, PAMAM dendrimer/DNA complexes were
used to encapsulate functional biodegradable polymer films for substrate mediated gene delivery.
Research has shown that the fast degrading functional polymer has great potential for localized
transfection.
Sensors
Scientists have also studied dendrimers for use in sensor technologies. Studied systems include
proton or pH sensors using poly(propylene imine), cadmium-sulfide/polypropylenimine
tetrahexacontaamine dendrimer composites to detect fluorescence signal quenching, and
poly(propylenamine) first and second generation dendrimers for metal cation photodetection
amongst others. Research in this field is vast and ongoing due to the potential for multiple
detection and binding sites in dendritic structures.
Dendrimer as Solubility Enhancers
There are many substances, which have a strong therapeutic activity but due to their lack of
solubility in pharmaceutically acceptable solvents have not been used for therapeutic purposes.
Water soluble dendrimers are capable of binding and solubilizing small acidic hydrophobic
molecules with antifungal or antibacterial properties. Dendrimers having a hydrophobic core and
a hydrophilic surface layer, have been termed unimolecular micelles. Unlike traditional micelles,
dendrimers do not have a critical micelle concentration. This characteristic offers the opportunity
to soluble poorly soluble drugs by encapsulating them within the dendritic structure at all
concentrations of dendrimer. A hydrophilic–hydrophobic core-shell dendrimer with PAMAM
interior and long alkane chain exterior was shown to bind 5-flurouracil, a water-soluble antitumor drug. After phospholipid coating of the dendrimer–fatty- acid macromolecule, oral
bioavailability in rats of 5-flurouracil was nearly twice the level of free 5-flurouracil. Dendrimerbased carriers could offer the opportunity to enhance the oral bioavailability of problematic
drugs. Propranolol, conjugated to surface-modified G3 PAMAM dendrimer, the solubility of
propranolol increased by over two orders of magnitude. Thus, dendrimer nanocarriers offer the
potential to enhance the bioavailability of drugs that are poorly soluble and/or substrates for
efflux transporters.
Blood substitution
Dendrimers are also being investigated for use as blood substitutes. Their steric bulk surrounding
a heme-mimetic centre significantly slows degradation compared to free heme, and prevents the
cytotoxicity exhibited by free heme.
Nanoparticles
Dendrimers also are used in the synthesis of monodisperse metallic nanoparticles.
Poly(amidoamide), or PAMAM, dendrimers are utilized for their tertiary amine groups at the
branching points within the dendrimer. Metal ions are introduced to an aqueous dendrimer
solution and the metal ions form a complex with the lone pair of electrons present at the tertiary
amines. After complexion, the ions are reduced to their zerovalent states to form a nanoparticle
that is encapsulated within the dendrimer. These nanoparticles range in width from 1.5 to 10
nanometers and are aptly called Dendrimer-Encapsulated Nanoparticles.
Dendritic Catalysts / Enzymes
The combination of high surface area and high solubility makes dendrimers useful as nanoscale
catalysts. Dendrimers have a multifunctional surface and all catalytic sites are always exposed
towards the reaction mixture. They can be recovered from the reaction mixture by easy ultra
filtration methods. Dendritic shells can be used to create a microenvironment favorable for
catalysis or provide shielding for functional groups at the dendritic core. Because of their
‘pseudo’-spherical nature and their resultant conformations the metal sites in these well-defined
polymeric catalysts should be easily accessible for substrate molecules and reagents, and
therefore exhibit characteristics- fast kinetics, specificity and solubility.
1. Metallodendritic catalysts
2. Catalysis with phosphine-based dendrimers
3. Catalysis with (metallo)dendrimers containing chiral ligands
4. Non-metal containing dendrimers
Industrial Processes
Dendrimers can encapsulate insoluble materials, such as metals, and transport them into a
solvent within their interior. Cooper and co-workers synthesized fluorinated dendrimers, which
are soluble in supercritical CO2 and can be used to extract strongly hydrophilic compounds from
water into liquid CO2. This may help develop Technologies in which hazardous organic solvents
are replaced by liquid CO2.
Nanocapsules and Dendrimers - Properties and Future Applications
Nanocapsules
A nanocapsule is any nanoparticle that consists of a shell and a space, in which desired
substances may be placed. Technologies for microencapsulating materials have been around for
several years, primarily for applications involving minimisation of hygroscopy and chemical
interactions, elimination of oxidation, and controlled release of nutraceuticals.
The Use of Man-Made Liposomes
Man-made liposome’s have been used in cosmetics for some years to control the release of
substances or protect them from the environment. Recently many other materials, such as
polymers, have been used to make nanocapsules.
The Properties of Polymeric Nanocapsules
Polymeric nanocapsules can be made in specific sizes, shapes, and in reasonable quantities.
Nanocapsules can be made to function in various ways. They can be produced as monodisperse
particles with exactly defined biochemical, electrical, optical, and magnetic properties. They
can be tailored to suit the complexity of whatever application they are intended for, such
causing the release of the contents in response to a particular bimolecular triggering mechanism
in targeted drug-delivery systems.
The Use of Nanocapsules as Smart Drugs
Nanocapsules can be used as smart drugs that have specific chemical receptors and only bind to
specific cells. It is this receptor that makes the drug ‘smart,’ allowing it to target cancer or
disease. The advantages of nano-encapsulation technologies for pharmaceutical applications
include:
•
Higher dose loading with smaller dose volumes
•
Longer site-specific dose retention
•
More rapid absorption of active drug substances
•
Increased bioavailability of the drug
•
Higher safety and efficacy
•
Improved patient compliance
The Future Benefits of Nanocapsules in Drugs
Beyond the ability to deliver existing drugs to their target, nanocapsules would allow for as
much as a 10,000-fold decrease in drug dosages, reducing the harmful side effects of drugs used
in chemotherapy. Quite often, drugs don’t make it to market is because they have too many
unwanted side effects. However, placing the same drug inside a nanocapsule and delivering it
directly to its intended target in a reduced dosage, eliminates some of those side effects, or at
least reduces them to an acceptable level.
Further Applications of Nanocapsules
Nanocapsules also have potential applications in agrochemicals, cosmetics, genetic engineering,
wastewater treatments, cleaning products, and adhesive component applications. They can be
used to encapsulate enzymes, catalysts, oils, adhesives, polymers, inorganic micro- and
nanoparticles, latex particles, or even biological cells.
Dendrimers as nanocapsules
A dendrimer is an artificially manufactured or synthesized large molecule comprised of many
smaller ones linked together - built up from branched units called monomers. Technically,
dendrimers are a unique class of a polymer, about the size of an average protein, with a
compact, tree-like molecular structure, which provides a high degree of surface functionality
and versatility. Their shape gives them vast amounts of surface area, making them useful
building blocks and carrier molecules at the nanoscale and they come in a variety of forms, with
different physical (including optical, electrical and chemical) properties.
Dendrimer as a Biologically Active Carrier
Dendrimers can act as biologically active carrier molecules in drug delivery to which can be
attached therapeutic agents and as scavengers of metal ions, offering the potential for
environmental clean-up operations because their size allows them to be filtered out with ultrafiltration techniques.
HYPERBRANCHED POLYMERS
Hyperbranched polymers are imperfect architectural relatives of dendrimers which have
pronounced similarities but also differences compared to the latter. For example, similar to
dendrimers, hyperbranched polymers have highly branched molecular architecture and a
multitude of reactive or non-reactive end-groups, but in contrst to dendrimers they do not contain
molecular core, have less defined intramolecular cargo space and often quite broad distribution
of molecular shapes and sizes.
Hyperbranched polymers are highly branched macromolecules with three-dimensional dentritic
architecture. Due to their unique physical and chemical properties and potential applications in
various fields from drug-delivery to coatings, interest in hyperbranched polymers is growing
rapidly.
Because of their architectural similarities, hyperbranched polymers have attracted
considerable research attention as possible cheaper alternatives to the more precise dendrimers.
This expectation was primarily based on the fact that in contrast to long multi-step reiterative
syntheses that both divergent and convergent approaches require for higher generation
dendrimers, resulting in high costs of labor and energy associated with repeated reaction and
separation procedures, hyperbranched polymers can be prepared by relatively simple, onepot-one-shot, relatively rapid polymerization reactions.
This technology uses “branched” monomers of the general type ABx where A and B
represent functional groups that can react with each other (i.e., A + B → -A-B-) but not with
themselves (i.e., A + A → no reaction and B + B → no reaction), while x is an integer equal or
larger than 2. For the simplest case of AB2 monomers, this polymerization can be represented as
shown in the following scheme:
Hyperbranched polymers have a very large number of branches. They can be prepared in
several ways, but most commonly from AB2 monomers or from combining A2 and B3
monomers. When prepared from AB2 monomers, gelation does not occur. The polymer
molecules have a single A terminus (the focus) and many B termini (the chain ends). Individual
monomers can react at 1, 2, or 3 sites. Monomers that react at only 1 site (the A site) have two
free B sites and are considered terminal (T). Monomers that react at 2 sites (the A site and 1 B
site) have one free B site and are considered linear (L). Monomers that have reacted at 3 sites
(the A site and both B sites) are considered dendritic (D). Hyperbranched polymers are
characterized by a degree of branching (DB) which represents the percentage of dendritic and
terminal monomers among the total monomers in the polymer:
DB = D + T/ (D + T + L)
Statistical treatments show that batch polymerization of AB2 monomers gives a DB of ~0.5.
Higher degrees of branching can be obtained using special reaction conditions (slow addition of
monomer, addition of a core). Perfect branching (DB = 1) can be found in the dendritic polymers
(see below).
Dendrimers are a subset of hyperbranched polymers in that they have no imperfections: they
branch at each monomer unit (DB = 1). Dendrimers also differ in method of preparation. They
are usually prepared by an iterative synthesis, with purification of intermediate stages or
"generations". This requires much effort, but allows for perfect branching. Hyperbranched
polymers are prepared in "one-pot" methods that result in imperfect branching.
Synthesis methodology
The synthetic techniques used to prepare hyperbranched polymers could be divided into two
major categories. The first category contains techniques of the single-monomer methodology
(SMM), in which hyperbranched macromolecules are synthesized by polymerization of an ABn
or a latent ABn monomer. According to the reaction mechanism, the SMM category includes at
least four specific approaches: (1) polycondensation of ABn monomers; (2) self-condensing
vinyl polymerization (SCVP); (3) self-condensing ring-opening polymerization (SCROP); (4)
proton-transfer polymerization (PTP).
The other category contains methods of the double monomer methodology (DMM) in which
direct polymerization of two types of monomers or a monomer pair generates hyperbranched
polymers.
1. SMM - polycondensation of ABn monomers
A broad range of hyperbranched polymers, including hyperbranched polyphenylenes,
polyethers, polyesters, polyamides, polycarbonates, and poly(ether ketone)s, are prepared via
one-step polycondensation of ABn type monomers. If one group of ABn monomers contains
double or triple bonds, small molecules may not be formed in the polymerization. Through
polyaddition of the ABn monomers, hyperbranched polyurethanes, polycarbosilanes,
polyamides, and poly(acetophenone)s have been successfully obtained. AB3, AB4, AB5, and
even AB6 monomers are also used to synthesize hyperbranched polymers while controlling the
branching pattern.
2. SMM—self-condensing vinyl polymerization
SCVP was invented by Fre´chet and coworkers in 1995. This polymerization method is quite
versatile, as hyperbranched polymers can be approached via polymerization of AB vinyl
monomers. In the reaction, the B groups of the AB monomers are activated to generate the
initiating Bp sites. Bp initiates the propagation of the vinyl group A in the monomer, forming a
dimer with a vinyl group, a growth site, and an initiating site. The dimer can function as an AB2
monomer, and undergo further polymerization to yield the hyperbranched polymer. In SCVP, the
activities of chain propagation of the growth sites and the initiating sites differ, resulting in a
lower DB when compared to the DB of the hyperbranched polymer prepared via
polycondensation of AB2 monomers. The theoretical maximum DB of SCVP is 46.5%. On the
other hand, SCVP does exhibit some disadvantages. For example, side reactions may lead to
gelation, the molecular weight distribution is usually very broad, and it is difficult to determine
DB directly via an NMR analysis.
3. SMM—self-condensing ring-opening and proton-transfer polymerizations
Hyperbranched polyamines, polyethers and polyesters have been prepared through
SCROP.
4. SMM-PTP (proton-transfer polymerization)- Hyperbranched polyesters with epoxy or
hydroxyl end groups and hyperbranched polysiloxanes were synthesized through PTP
(proton-transfer polymerization).
Scientists have developed an impressive alternative technology for the preparation of
hyperbranched polymers by the bimolecular non-linear polymerization, BMNLP. Just like the
traditional monomolecular polymerizations of ABX monomers, BMNLP also utilizes a stepgrowth reaction mechanism, but in contrast to the former, it involves, two reactive monomers AX
and BY, where A and B also denote two types of mutually reactive functional groups, while x and
y are integers which must both be equal to or larger than 2, while one of them (either x or y)
must be equal to or larger than 3. Thus, the most common BMNLP systems include A2 + B3, A2
+ B4, and A3 + B4 monomer combinations. In general, the simplest of these, the A2 + B3 system,
in which the minor component has completely reacted, can be represented as shown in the
following scheme:
The essential and common feature of all BMNLP systems is the need for careful control of the
polymerization process, by appropriate selection of the relative concentrations of the reacting A
and B groups and the extent of the reaction, in order to prevent their natural tendency to crosslink
to a gel.
BMNLP reactions offer some important advantages over traditional ABX polymerization
systems.
(i)
(ii)
(iii)
the extreme versatility of the process to yield a practically unlimited variety of
polymer compositions from a vast number of commercially available monomers,
the unique ability to produce compositionally identical polymers, -[AB]n<, with
different (A or B) end-groups, and
the complete elimination of the monomer shelf-life problems that are often
encountered with many ABX compounds which can polymerize either without the
need for reaction catalyst or under less stringent storage conditions.
Utilizing the BMNLP approach, we have developed and patented a wide variety of
different hyperbranched polymers, including polyamides, polyamidoamines,
polyureas, polyurethanes, polyesters, polycarbosilanes, polycarbosiloxanes,
polycarbosilazanes, perfluorinated derivatives of many of the preceding polymers,
etc.
They are ideally suited for a variety of specialty coating applications including antimicrobial,
antifouling and decontamination coatings, superhydrophobic and superhydrophilic coatings,
chemical and biological sensors, semipermeable membranes, electronic and photonic parts and
materials, etc.