Elements of Polymer Science
E. Desmond Goddard, James V. Gruber in Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
where n is an integer, called degree of polymerization of this macromolecule. Before 1930, polymer molecules were generally considered as physical aggregates of unchanged monomer molecules , so-called association colloids. However, already in 1920, Staudinger had postulated that these colloidal particles were composed of a single, very long molecule, a macromolecule. This revolutionary concept paved the way for synthetic organic chemists, in particular Carothers, to start building such macromolecules in a systematic way from known monomers. Since the , many thousands of polymers have been prepared, but less than 100 of them have reached the phase of large-scale industrial production. For accounts of the history of polymer science and technology, see, for example, Refs. 1 and .
Uro-Angiographic Contrast Agents—The Holy Grail
Christoph de Haën in X-Ray Contrast Agent Technology, 2019
Polypaque, a particular realization of a certain chemical class of polymers, merit some critical evaluation not only as focal points for human group dynamic phenomena in technology shaping but also as molecules and contrast agents. Polypaque was described as a polymer of presaponified metrizoic acid of unrevealed exact chemical constitution (Almén and Fondberg [1966] 1967; Almén 1966a). Its degree of polymerization lay between 150 and 300 and the corresponding molecular weight between 100,000 and 200,000 (Almén 1966a). Fondberg let me know that the macromolecules were weakly cross-linked. A solution of the compound at a concentration of 440 mg (Iodine)/mL was reported to have a dynamic viscosity of 0.013 Pa·s. Almén did not question this puzzlingly small value since, as already pointed out, on erroneous theoretical grounds, he was not expecting viscosity to be a problem. Most notably, Almén described rudimentary observations on a single, unnamed human volunteer who had been injected with the compound. In the aforementioned contacts, I had with Fondberg he declared the viscosity data in error and himself as the volunteer. The polymer was reportedly degraded in the volunteer’s blood and was excreted completely within 24 h. Similar observations in animals were also reported on some other members of the polypaque family (Almén and Fondberg [1966] 1967). No radiographs obtained with these contrast agent solutions were made available.
Adjuncts in Vitreoretinal Surgery
Pradeep Venkatesh in Handbook of Vitreoretinal Surgery, 2023
The viscosity of a substance is the resistive force that is encountered when a liquid is forced through a narrow tube. It is dependent on the molecular weight and degree of polymerization of the substance. It is measured as centistoke (cs). Generally, the higher the molecular weight, the greater the viscosity. During vitreoretinal surgery, the role of viscosity is most evident during injection and removal of silicone oil. The higher the viscosity of silicone oil, the greater the force necessary to inject and remove the oil from the vitreous cavity. This is the reason that 5000 cs of silicone oil is more difficult to inject and remove than 1000 cs of oil. Hence, 1000 cs of oil is preferred during uncomplicated surgery. However, higher viscosity oil has a lower risk of emulsification. Hence, in situations wherein it is deemed necessary to retain oil for longer periods [e.g., resurgery in one-eyed patients, choroidal coloboma–associated retinal detachment, retinal detachment in patients with oculocutaneous albinism], 5000 cs of oil is preferred.
A novel multi-stimuli-responsive theranostic nanomedicine based on Fe3O4@Au nanoparticles against cancer
Published in Drug Development and Industrial Pharmacy, 2020
Bakhshali Massoumi, Amir Farnudiyan‐Habibi, Hossein Derakhshankhah, Hadi Samadian, Rana Jahanban-Esfahlan, Mehdi Jaymand
The successful block copolymerization of acrylic acid monomer onto (S-PNIPAAm)2 was confirmed through the appearance of a broad chemical shift at 12.35–12.65 ppm related to –COOH group (l). It is worth noting that the chemical shifts of methylene and methine groups (j and k) of PAA backbone were overlapped with the methylene and methine groups of PNIPAAm backbone and appeared at 1.35–2.20 ppm. The degree of polymerization (DPn) and number-average molecular weight (Mn) of the synthesized polymers were calculated from the 1H NMR data through the following equations:
Antioxidative protection of haemoglobin microparticles (HbMPs) by PolyDopamine
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Olga Baidukova, Quan Wang, Saranya Chaiwaree, Dorette Freyer, Ausanai Prapan, Radostina Georgieva, Lian Zhao, Hans Bäumler
PD as the major pigment of eumelanin, typically shows broad-band absorption ranging from the ultraviolet to the visible region [27]. Hong et al. reported the characteristic absorption peaks at 283 nm corresponding to the catechol moiety in the dopamine monomer. The peaks at 330 nm were observed as the reaction processed because of the oxidation of the catechol groups [28]. Since the results as shown in Figure S1 of the supporting information suggested a linear relationship between the concentration of PD and absorption values at 320 nm, the concentration of PD attached to the HbMPs particles was determined by the absorption values at 320 nm after washing steps to remove the excess dopamine or PD. The results presented in Table 1 showed increasing the initial concentration of dopamine does apparently help with the amount of PD on the substrates. The amount of PD in one particle demonstrated higher polymerization from PD-HbMPs 1 to PD-HbMPs 3. It should be noted that the degree of polymerization with same reaction time is 75%, 58% and 26% for PD-HbMPs 1, PD-HbMPs 2 and PD-HbMPs 3, respectively.
Co-processing of small molecule excipients with polymers to improve functionality
Published in Expert Opinion on Drug Delivery, 2021
Prashantkumar K. Parmar, Srilaxmi G. Rao, Arvind K. Bansal
The degree of polymerization and substitution of the polymer can affect disintegration property. Sodium carboxymethyl cellulose (NaCMC) with high molecular weight and lower level of carboxymethylation exhibited better disintegration potential [16]. Corn starch contains different ratio of amylose (linear chain) and amylopectin (complex-branched chain), which is responsible for disintegrant and binding properties, respectively. Besides, porosity of the tablet was not affected by varying the ratio of amylose to amylopectin [17]. The degree of cross-linking and extent of substitution of the polymer can affect disintegration action. The swelling of sodium starch glycolate (SSG) was inversely proportional to a major extent on the degree of cross-linking and a lesser extent on the level of substitution [18].
Related Knowledge Centers
- Copolymer
- Macromolecule
- Oligomer
- Polymer
- Structural Unit
- Repeat Unit
- Carothers Equation
- Chain-Growth Polymerization
- Kinetic Chain Length
- Chain Termination