# Evidence: polymer hydration

Parent: — · class: solution behaviour · names merged here: polymer hydration

3 papers measured or used it, 0 only mentioned it (of 207 kept papers). Papers in year order; each section heading ends with the paper's category / subcategory. Generated by tools/build_evidence.py from registry/concepts.csv and the cards; do not edit.

## 2024 Bapat — Interplay of Drug−Polymer Interactions and Release Performance for HPMCAS-Based Amorphous Solid Dispersions · Dissolution / A. Release mechanism and LoC

[2024-bapat-hpmcas-drug-polymer-complexation-release-performance](../../../cards/2024-bapat-hpmcas-drug-polymer-complexation-release-performance/paper.html) · Dissolution / A. Release mechanism and LoC · used · as: polymer hydration

| id | kind | content | locator |
|---|---|---|---|
| C24 | claim, prior hypothesis, authors: asserted | Glassy polymers dissolve by water ingress, plasticization, rising mobility and diffusion of hydrated chains if solvent quality is sufficient; protonated HPMCAS interacts little with water, so a critical extent of ionization, and hence a threshold pH, is needed before it dissolves [rests on: argument only] | p.1473 |
| C25 | claim, mechanism, authors: "is expected" | A lipophilic drug lowers the rate and extent of ASD hydration, so higher DL is expected to delay release of the ASD components by reducing polymer dissolution, as seen in Figs. 2 and 3 [rests on: R2, R3] | p.1473 |
| C28 | claim, mechanism, authors: "likely"; "are expected" | For the low-complexation drugs the lower release at higher DL is likely due mainly to drug lipophilicity through less hydration; these drugs are expected to interact weakly with ionized HPMCAS, although some insoluble complex forms, more at higher ratios [rests on: R14, R12] | p.1473-1474 |

## 2025 Bapat — Impact of HPMCAS Grade on the Release of Weakly Basic Drugs from Amorphous Solid Dispersions · Dissolution / A. Release mechanism and LoC

[2025-bapat-hpmcas-grade-weak-base-asd-release-complexation](../../../cards/2025-bapat-hpmcas-grade-weak-base-asd-release-complexation/paper.html) · Dissolution / A. Release mechanism and LoC · used · as: polymer hydration

| id | kind | content | locator |
|---|---|---|---|
| C2 | claim, prior hypothesis, authors: asserted | Critical ionization fraction model: an acidic polymer starts to dissolve only after a critical fraction of its ionizable groups is ionized, and its rate then rises with further ionization; ionization to carboxylate enhances hydration, plasticization and dilution of the chains [rests on: cited: refs 45, 46] | p.397 |
| C3 | claim, prior hypothesis, authors: "can impact" | Anything that hinders polymer hydration, for example a hydrophobic drug interacting strongly with the carboxylate ion in the ASD, can impact polymer solubility and dissolution rate [rests on: argument only] | p.397-398 |
| C26 | claim, mechanism, authors: "fairly straightforward to rationalize" | LF has twice as many COOH per gram as HF, so the lower impact of the drug on LF release is straightforward to rationalize: LF is more soluble at pH 6.8 and, at 25% DL, has more carboxylates, leaving spare carboxylates not bound to the cationic drug to contribute to hydration [rests on: M3, M5, R2, R3] | p.403 |

## 2025 Kaur — Impact of drug-polymer complexation and media properties on the release performance of amorphous solid dispersions containing a weakly basic drug and hydroxypropyl methylcellulose acetate succinate · Dissolution / A. Release mechanism and LoC

[2025-kaur-bdq-hpmcas-complexation-media-asd-release](../../../cards/2025-kaur-bdq-hpmcas-complexation-media-asd-release/paper.html) · Dissolution / A. Release mechanism and LoC · used · as: polymer hydration

| id | kind | content | locator |
|---|---|---|---|
| C46 | claim, mechanism, authors: "may play a role"; "is expected to impede" | This traces back to the critical ionization of about 77% estimated for HPMCAS-MF; hydration resulting from ionization, rather than ionization itself, solubilizes the chains (charge repulsion may play a role); complex formation does not interfere with ionization but is expected to impede hydration and hence plasticization, chain dilution and release [rests on: C28; argument only] | p.10 |
| C3 | claim, prior hypothesis, authors: "have also been proposed"; "It was suggested"; "supported the conjecture" | Drug-polymer ionic interactions have been proposed to impede polymer release from enteric polymers: lumefantrine (pKa 8.7)-HPMCAS ASDs released poorly at pH 6.8 through ionic interactions that impede hydration of carboxylate groups; lipophilic cationic drugs reduce HPMCAS solubility through a hydrophobic electrostatic complex at the gel-layer interface and in solution, giving poor release even at 5% DL [rests on: cited: refs 11, 16] | p.2 |