Different Types Of Polymers Pdf 11 [TOP]
Polymers may be naturally found in plants and animals (natural polymers) or may be man-made (synthetic polymers). Different polymers have a number of unique physical and chemical properties, due to which they find usage in everyday life.
Different Types Of Polymers Pdf 11
Polymers cannot be classified under one category because of their complex structures, different behaviours and vast applications. We can, therefore, classify polymers based on the following considerations.
The structure of polymers containing long and straight chains falls into this category. PVC, i.e. poly-vinyl chloride, is largely used for making pipes and electric cables is an example of a linear polymer.
Most of the polymers around us are made up of a hydrocarbon backbone. A Hydrocarbon backbone is a long chain of linked carbon and hydrogen atoms, possible due to the tetravalent nature of carbon.
A few examples of a hydrocarbon backbone polymer are polypropylene, polybutylene, and polystyrene. Also, there are polymers which, instead of carbon, have other elements in their backbone. For example, Nylon, contains nitrogen atoms in the repeated unit backbone.
The polymers which are degraded and decayed by microorganisms like bacteria are known as biodegradable polymers. These types of polymers are used in surgical bandages, capsule coatings and in surgery. For example, Poly hydroxybutyrate co vel [PHBV]High-Temperature PolymersThese polymers are stable at high temperatures. Due to their high molecular weight, these are not destroyed even at very high temperatures. They are extensively used in the healthcare industries, for making sterilization equipment and in the manufacturing of heat and shock-resistant objects.
Polyethene: It is the most common type of plastic found around us. Mostly used in packaging from plastic bags to plastic bottles. There are different types of polyethene, but their common formula is (C2H4)n.
These polymers possess high strength and resistance to chemical, thermal, and abrasion, similar to ceramics and metals for use in engineering applications. Examples: Silicone, Polycarbonate, ABS, and Polysulfone.
These polymers occur naturally in nature and are found in plants and animals. Additionally, there are also biodegradable polymers called bipolymers. Examples included starch, proteins, rubber, and cellulose.
These polymers are completely man-made. Plastic as we use commonly is the most broadly used synthetic polymer. Synthetic polymers are used in industries and several dairy products. Examples include polyether, nylon-6, 6, 6, etc.
In Addition Polymerization, molecules of the same or different monomers add up together on massive scales to form polymers. These monomers are unsaturated compounds like alkenes, alkadienes, and their respective derivatives.
A few examples of a hydrocarbon backbone polymer are polystyrene, polypropylene, polybutylene. Also, there are polymers that instead of carbon have other elements in their backbone. For example, Nylon has nitrogen atoms in the repeating unit backbone.
Polymers are macromolecules that are formed by repeating structural units on a massive scale. The repeating units are made up of monomers that are simple and reactive molecules. These units have covalent bonds. Polymerisation is this formation of polymers from their respective monomers.
Polymers are macromolecules that are formed by repeating structural units on a massive scale. The repeating units are made up of monomers that are simple and reactive molecules. Based on the monomers, polymers can be classified as homomers and heteropolymers.
Natural Polymers: These polymers occur naturally in nature and are found in plants and animals. Additionally, there are also biodegradable polymers called bipolymers. Examples included starch, proteins, rubber and cellulose.
Synthetic Polymers: These polymers are completely man-made. Plastic as we use commonly is the most broadly used synthetic polymer. Synthetic polymers are used in industries and several dairy products. Examples include polyether, nylon-6, 6,6 etc.
Metallic, organic, inorganic and polymeric nanostructures, including dendrimers, micelles, and liposomes are frequently considered in designing the target-specific drug delivery systems. In particular, those drugs having poor solubility with less absorption ability are tagged with these nanoparticles [17, 29]. However, the efficacy of these nanostructures as drug delivery vehicles varies depending on the size, shape, and other inherent biophysical/chemical characteristics. For instance, polymeric nanomaterials with diameters ranging from 10 to 1000 nm, exhibit characteristics ideal for an efficient delivery vehicle . Because of their high biocompatibility and biodegradability properties, various synthetic polymers such as polyvinyl alcohol, poly-l-lactic acid, polyethylene glycol, and poly(lactic-co-glycolic acid), and natural polymers, such as alginate and chitosan, are extensively used in the nanofabrication of nanoparticles [8, 30,31,32]. Polymeric nanoparticles can be categorized into nanospheres and nanocapsules both of which are excellent drug delivery systems. Likewise, compact lipid nanostructures and phospholipids including liposomes and micelles are very useful in targeted drug delivery.
Thus, nanotechnology offers multiple benefits in treating chronic human diseases by site-specific, and target-oriented delivery of medicines. However, inadequate knowledge about nanostructures toxicity is a major worry and undoubtedly warrants further research to improve the efficacy with higher safety to enable safer practical implementation of these medicines. Therefore, cautiously designing these nanoparticles could be helpful in tackling the problems associated with their use. Considering the above facts, this review aims to report different nano based drug delivery systems, significant applications of natural compound-based nanomedicines, and bioavailability, targeting sites, and controlled release of nano-drugs, as well as other challenges associated with nanomaterials in medicines.
The integration of therapy and diagnosis is defined as theranostic and is being extensively utilized for cancer treatment [44, 45]. Theranostic nanoparticles can help diagnose the disease, report the location, identify the stage of the disease, and provide information about the treatment response. In addition, such nanoparticles can carry a therapeutic agent for the tumor, which can provide the necessary concentrations of the therapeutic agent via molecular and/or external stimuli [44, 45]. Chitosan is a biopolymer which possesses distinctive properties with biocompatibility and presence of functional groups [45,46,47]. It is used in the encapsulation or coating of various types of nanoparticles, thus producing different particles with multiple functions for their potential uses in the detection and diagnosis of different types of diseases [45, 47].
Choi et al.  also synthesized nanoparticles of hyaluronic acid with different diameters by changing the degree of hydrophobic replacement of HA. The nanoparticles were systemically administered in the mice with tumor, and then, its effect was studied. This same research group developed a versatile thermostatic system using poly (ethylene glycol) conjugated hyaluronic acid (P-HA-NPs) nanoparticles for the early detection of colon cancer and targeted therapy. To assess the effectiveness of the nanoparticles, they were first attached to the near-infrared fluorescent dye (Cy 5.5) by chemical conjugation, and then, the irinotecan anticancer drug (IRT) was encapsulated within these systems. The therapeutic potential of P-HA-NP was then investigated in different systems of the mice colon cancer. Through the intravenous injection of the fluorescent dye attached nanoparticles (Cy 5.5-P-HA-NPs), minute and initial-stage tumors as well as liver-embedded colon tumors were efficiently pictured using an NIRF imaging method. Due to their extraordinary capability to target tumors, drug-containing nanoparticles (IRT-P-HA-NP) showed markedly decreased tumor development with decreased systemic harmfulness. In addition, healing effects could be examined concurrently with Cy 5.5-P-HA-NPs .
In this context, drug designing has been a promising feature that characterizes the discovery of novel lead drugs based on the knowledge of a biological target. The advancements in computer sciences, and the progression of experimental procedures for the categorization and purification of proteins, peptides, and biological targets are essential for the growth and development of this sector [66, 67]. In addition, several studies and reviews have been found in this area; they focus on the rational design of different molecules and show the importance of studying different mechanisms of drug release . Moreover, natural products can provide feasible and interesting solutions to address the drug design challenges, and can serve as an inspiration for drug discovery with desired physicochemical properties [3, 69, 70].
On the other hand, stimuli-responsive nanocarriers have shown the ability to control the release profile of drugs (as a triggered release) using external factors such as ultrasound , heat [97,98,99], magnetism [100, 101], light , pH , and ionic strength , which can improve the targeting and allow greater dosage control (Fig. 2). For example, superparamagnetic iron oxide nanoparticles are associated with polymeric nanocarriers  or lipids  to initially stimulate a controlled release system by the application of external magnetic field. In addition, Ulbrich et al.  revised recent achievements of drug delivery systems, in particular, on the basis of polymeric and magnetic nanoparticles, and also addressed the effect of covalently or noncovalently attached drugs for cancer cure . Moreover, Au/Fe3O4@polymer nanoparticles have also been synthesized for the use in NIR-triggered chemo-photothermal therapy . Therefore, hybrid nanocarriers are currently among the most promising tools for nanomedicine as they present a mixture of properties of different systems in a single system, thus ensuring materials with enhanced performance for both therapeutic and diagnostic applications (i.e., theranostic systems). Despite this, little is known about the real mechanisms of action and toxicity of drug delivery systems, which open opportunity for new studies. In addition, studies focusing on the synthesis of nanocarriers based on environmentally safe chemical reactions by implementing plant extracts and microorganisms have increased .